There is a point towards the end where you say, "There comes a point where the only way to increase the speed of the object is to turn the object into light." But, I believe a better way of saying that would be, "There comes a point where the only way to increase the speed of the object is to turn the object into something with no mass."
Yes, it's the ultimate trade-off! Either you are at "rest" with all motion through time, or have no mass so that all motion is through space (no time passes for you).
It’s almost like mass creates a hole in space that space coagulates to patch/spackle - like a hole in the wall. And that greater density of coagulating space slows down time which results in geodesics whereby the slowest time is also the lowest-energy state that an object in a gravitational field defaults to.
The man, the myth, the legend himself! Thanks for watching, Tay. I like that analogy, I think of the formation of mass as basically just this, something like a knot tied into spacetime that pulls space inwards in all directions (at the speed of light), and which in some abstract way stretches out time as well.
atoms are mostly empty space. Matter does displace space, which pushes back against the matter as it passes through it. This causes a higher density region around the mass. Essentially, gravity is the effect of spatial pressure. We aren’t pulled towards the earth, we are pushed down onto it by space. So why time dilation? Time is just the rate of quantum vibration. In a high density special field, the vibration is slowed, ergo, time is slowed.
E=MC2 is just a joke.., First off we live in a magnetic world. E=MD (Magnetic Density), All mater is magnetic all plants people everything we know exist is magnetic. The center of a magnet will prove all this to you!! Start working with the center of a magnet and you will see many things , Anti Gravity is one.. When Tesla tested his tower in Colorado for the first time he sent too much power from space into the local power plant and blew up one of the generators. FACT.. The north and south poles are the weakest part of a magnet, The energy in the middle once you learn how to use it will blow your mind!
I have always thought of mass in this way since I was little and wondered about the stars. As I was told about gravity, I thought of it as every massive object sort of has "pushed space out of the way" to occupy that space, and that is why objects have any kind of effect on eachother to begin with.
Holy crap, I've had an amateur interest in relativity for 30 years but I've never understood gravity as a function of movement through spacetime like this before. Thanks so much, cool as hell.
I found Science Clic to be an amazing resource too. Similar descriptions: ruclips.net/video/wrwgIjBUYVc/видео.html ruclips.net/video/GQZ3R81iyE0/видео.html but there's a bunch of other videos there that are great. But I think this video indeed goes into even more detail.
The presentation still left out issue of weight!!! He something are not very clear, but it should be accepted as their are till proof otherwise. Alright.
What is offered in this video is a different description than the usual one. This is due to your starting question: what causes gravity? Answer: time dilation. And this video does a fine job in answering that question. The usual starting question from a historical perspective was: what causes time dilation? Answer: gravity. Each of these descriptions are equivalent. And that was the genius of Albert Einstein.
Only the theory presented is supposed to do away with gravity as a force, as I understand it… Also how is mass defined in the absence of gravity? As inertia? Sort of a resistance against acceleration? It also seems to me that time would come out a space-vector - the path of least resistance between two locations in a three dimensional grid - which, to complicate matters further, is itself warped by all the masses in the vicinity in accordance with their masses. Nevertheless, NASA must have precise, time proven methods by which to calculate these things. How else would they be able to slingshot objects around planetary bodies, as they often do? NASA can’t presumably rely on approximations, since last minute course-corrections would come too late, when their space probes is light-weeks away. Couldn’t you start by covering how such calculations are done in real life before we let ourselves be overwhelmed by quantum conundrums?
Einstein described very well in the chapter "The Equality of Inertial and Gravitational Mass" of his popular book "Relativity: The Special and General Theory" the conundrum that experimentally it had been determined that inertial mass of an object is equal to its gravitational mass to a high degree of precision. Einstein's realization was that this equivalence might not be accidental. The fact that the gravitational "mass" exactly cancels out the inertial mass in the Newtonian equation for acceleration due to gravity indicates a purely geometric phenomenon behind gravitational acceleration. In other words, the "force" of gravity is fictitious, but the geometry is not what we thought it was.
@@IldarSagdejev I have the book and have read it a couple of times with great pleasure, so no! That’s not what Einsteins says. He just states that there’s no way to discern gravitational acceleration from an equal acceleration by an equal force, unless you have some external reference, thus explaining why inertial mass and weighed mass must be one and the same. The theory about distorting the space/time matrix came almost 20 years after Relativity was published and seems to treat time as a space-vector, which makes things more complicated to calculate, and as you know, a breakthrough usually means better and more generalized formulas. But time, handled as a vector, must itself be distorted by mass, so how can NASA successfully calculate sling-shooting anyway?
By far the best explanatory video on the internet on the subject!! Thank you for this wonderful feeling of deeper and intuitive understanding of gravity!
So if gravity is the difference in time dilation between 2 points that are different far away from the center of gravit, how can gravity work on an object that is flat?
Perhaps the reason that mass creates time dilation thus causing gravity is that as the universe expands the momentum of mass is holding it back from expanding at the same rate as empty space and therefore gravity.
Simplicity is the key to understanding the notion of inertial reference frames and to understand euclidian space. Cool diagrams are important and you’ve nailed it here.
I had been trying to formulate a construct about the synonynous nature of Gravity and time, which was mainly because of seeing a comment that so physicists believe that gravity is nothing but time!. That intuitively made a lot of sense to me. What I used to think/speculate before watching this video was how time seems to be constraining the motion of an object in space and somehow making it cover a hyperbolic path which ofcourse tends to send the object towards another object. I thought Time does it because of it being different in behaviour than than the Space coodinates. An object can move back and forth in space but cannot move backwards in time. Additionally, time passes at a constant rate, and, any change in the movement of an object in space does change this rate of passage of time for that object!. Your illustration of controtion of space-time in a geodesic into an energetically favourable geodesic path was new to me and helped me piece my ideas together. Thanks for the video, it was beautifully described. I still wonder whether acceleration of an object towards another massive object being constant ( for instance g= 9.8 m/s²) is a sign of restriction of motion of an object in space because of the constant nature of passage of time. I would love to hear your thoughts (and also correct me if I made a mistake in comprehending something).
This channel must rise up! This single video filled many gaps that I've been thinking about, even after all that very same great references (PBS, Eugene, Asylum and ScienceClic). I found it searching "gravity and entropy", and I hope I can find something about it around here. Thank you!
Excellent explanation of how gravity works. Much better than the three videos you mentioned in the beginning. I would love it if you expanded your examples of traveling through the geodesics to objects flying by a planet at different speeds. Explaining why speed matters and why traveling at different speeds determine the geodesic path of the object. At high speeds its path is slightly bent. At the right speed it winds up in orbit. At lower speeds it crashes into the planet.
Amazing, I've never seen it described like this! It makes so much sense to think of my inertia as me being attached to spacetime due to the way my mass warps it. Bravo
Yea that’s so believable, seems super logical, as long as you forget all knowledge ever known! Disregard everything ever felt, seen, heard, learned….-all sensible perceptions. Totally plausible! If that was no feat to overcome, then this wont be any brain-buster either…. Here soon the democrats will quit destroying the country, by funding good police and defund the wef, un, Soros, and their malnourished skinny Jeaned antifa creeps!
This seems like a great explanation, until you realize that: A) nothing is moving faster through time, rather the planes of simultaneity of the accelerated observers on earth are merely rotating with respect to the higher-up observers. B) the geodesics don’t “bend” into space; the ground is merely accelerating towards them, and you’re drawing them from an accelerated frame of reference C) indeed since the diagram drawn is for a uniform gravitational field, we can perform a simple coordinate transformation so that our “bent” geodesics will be straight once more, ultimately demonstrating that D) a uniform gravitational field has ZERO curvature and therefore exhibits no warping of spacetime. E) Meanwhile, a non-uniform gravitational field does have curvature; plotting this on a spacetime diagram and you would see that geodesics diverge or converge towards one another. Changing separation between geodesics is real curvature, i.e., tidal forces, which is real gravity. It was a good video, but sorry, curved lines on a spacetime diagram do not equate to spacetime curvature.
I dont think any better video of explanation of Spacetime is available on internet. Its awesome. Very well and simplistically explained. Would like to see such videos on quantum mechanics too if by any chance u prefer to make. Thanks a lot
"because things pass through time at different speeds at different elevations. " I have watched HOURS of gravity RUclips videos to finally find this sentence. THANK YOU!
Finally, I’ve been trying to understand the curvature of space time for a very long time and this explanation is beautiful, this is just so amazing to me and the fact that Einstein figured all of this out on his own is amazing to me. Best explanation I’ve seen, I finally understand, thank you so much. This is so cool and it is such an amazing way to think about gravity
Einstein's work here was absolutely astounding, but he didn't do it alone! The work of his advisor, Hermann Minkowski, and the work of Lorentz were indispensable in his development of special and general relativity.
We love this video! You’re right that the connection between time dilation and gravity is only made more confusing by the “gradient flow” analogies of other videos. And we like that you’re not afraid to tackle the big questions - “why does mass warp spacetime” is the essential mystery left behind in the wake of GR. Interesting to think, for instance, that an accelerating object, in consequence of the equivalence principle, must observe a gravitational field, i.e. warped spacetime, in the vicinity of itself, and that the strength of this field is independent of both its mass and velocity. Great work, we look forward to your future videos!
"... an accelerating object, in consequence of the equivalence principle, must observe a gravitational field, i.e. warped spacetime, in the vicinity of itself, and that the strength of this field is independent of both its mass and velocity." Well, lets do some philosophy. The only two entities in your statement that pretend to be real are the accelerating object and the act of observation of some object which is different, i.e. on the outside, from this observing and accelerating object. In this case, one may say that the observed object is the exterior, should we say the outside, of observing object. However, according to GR equivalence principle nither the accelerating object nor the gravitational field are real, therefore "the strength of this field is independent of both mass and velocity". Actually the only two real entities in your statement are the change of the rate of change, which is real because of it"s actual limit /the speed of light/ and the continuity of the extension /or the duration/. Just forget about the force and strength.
I was commenting on a video just yesterday on how the warped 2d net in so many videos give you an incorrect picture of what is actually happening, since the warpage of spacetime would take pace in all directions at once. I give you credit for showing this warpage in a more true to life model. Thanks!
Thanks! I'd like to add that the visualization at 10:43 is by the channel ScienceClic, I neglected to include a credit there (my bad!). (Their channel is superb)
The best explanation of how time dilation is a symptom of warped spacetime which itself causes gravity (i.e. why objects accelerate towards the earth. Thank you so much as have been trying to get for over a year now 😄
This is probably the cleanest explanation I've seen in any medium. Bravo! (I had two GR courses in grad school. I've read most of the graduate-level GR textbooks, and read fairly recent research papers...and Kip Thorne's office is a few minute walk from mine). I would just point out that energy is the thing that causes time dilation somehow (energy density, more specifically). Mass just happens to be a compact form of energy. The deep connection between energy and time might be a hint pointing us toward understanding why energy density slows time.
Huge thanks, Dr. Stickley! Very much appreciated coming from you. Re. “The deep connection between energy and time might be a hint pointing us toward understanding why energy density slows time”, I’ve been playing around with the idea that spacetime warping is due to the density of particle interaction in a given region of spacetime alongside the need for relative positions and momenta needing to maintain a relativistic relationship to the speed of light. In other words, mass could be thought of as an emergent property (due to spacetime warping) that arises out of the interaction of e.g. fermions and bosons, and is not itself a fundamental property that particles (or energy) have. In simple terms, the more boson/fermion interactions, the more spacetime needs to be “knit” by those interactions into a web that maintains relative positions and momenta relative to the speed of light always being constant. The seed of this idea is the observation/hypothesis that only some interaction can define a particle’s location and trajectory in spacetime; absent these interactions, the particle exists as a spread-out “impulse” in the quantum fields, quantified in our framework by its probability amplitude. I dug a little into particle physics to flesh this intuitive idea out and learned that I’m way out of my depth there. Something I’ll probably continue pondering, though.
@@IdeaListEye The current standard explanation for what creates mass is the Higgs mechanism; things acquire mass by interacting with the Higgs field, but this interaction is only responsible for a small part of a particle's mass; it's enough to keep the particle from moving around at c like a massless particle, but most of the measured mass of a particle comes from field energy (i.e., the swarm of virtual particles) around the particle. For an electron, most of the mass is due to energy in the electromagnetic field, since electrons have electric charge which binds to the electromagnetic field; for a quark, the mass is mostly due to the energy in the gluon field, since quarks have color charge which binds to the gluon field. The mass of composite particles, like protons is mostly due to the kinetic energy of the quarks it contains, plus the energy stored the gluon field and electromagnetic field. Some people think that inertia may be due to the Unruh effect. I've been in favor of that general view since high school. This seems pretty similar to what you've been thinking about. Do a Google search for "is inertia due to the unruh effect?" to find out more. I've also been playing with the idea that the rate of time passage in a region of space is somehow inversely related to the density of interactions in that region of space. I haven't been able to flesh it out into an actual theory, though. If it can be done, then gravity emerges as a direct consequence, so it would be a big deal. You might also find "loop quantum gravity" to be interesting....there are some interesting ideas there, even if it doesn't turn out to be the way nature works.
I've watched soo many videos about general relativity. Those may have planted some seeds, but these 10 minutes made a bigger impact on my understanding than the many hours that preceded them.
Beautiful, it shows a dynamic space product of the energetic presence (see the previous comment for the quantum approach), so gravity potential energy is equivalent to the kinetic energy of speed √[2GM/R], Schwarzschild time dilation is equivalent exact to Lorentz dilation. The relativistic view is the union of observable speed plus the equivalent gravitational speed! This and more can be read in a small amazon book "Space, main actor of quantum and relativistic theories". Thanks for your great videos
One thing I wished you had explained regards the stumbling block I had when I first tried to understand time dilation. I could not get my mind around the fact that two old school mechanical clocks would show different times when one was moved away from the earth. It seemed like they made a mistake as the mechanical mechanism should give the same result. The glossing over the reason this happens at an atomic level is not usually explained and causes a headache when trying to put the whole picture together. Maybe a topic for a future video? André in Sydney
This has been a consideration from the start, and a lot of very smart people have taken great pains to address it (and to test what you proposed, whether it's just a mechanical accident or actually a consequence of fundamental physics). You can read more here: en.wikipedia.org/wiki/Experimental_testing_of_time_dilation
I have spent so many pleasant hours thinking about this much like you have shown here. But the second part of it I hadn't thought about, more that I accepted that all objects follow the fastest path or the one of least resistance. Great video, thanks.
I've had a life long obsession with this subject and have come to the same conclusion that you have. Your video however has deburred the rough edges of my thinking and really brings the idea into focus, in a way that, so far as I know, is unmatched. My only disappointment is that you didn't illustrate the mechanism in which mass causes this effect in spacetime but my forgiveness is gratuitous, being that it's a very difficult problem to solve.
Mind-bending video ! 😉 I have been looking for this visual explanation for a while, and I was not satisfied with the videos you list in your introduction. Now I know why it takes effort to climb up stairs!
Glad you liked it! I would like to post more, but I've been busy with other things lately. Hopefully soon- do you have any topics in mind you would like to see explored?
@@IdeaListEye I previously visualized the warping of curvature as static around the mass, rather than as a dynamic/continuous motion of being sucked in. I’ve been ruminating on.. where this spacetime goes for lack of a better phrase. It just keeps getting sucked in? Maybe not enough for a whole video but the illustrations you used were so helpful to see in 3d vs the more common 2d depiction. I also think length contract doesn’t get as much love on youtube as time dilation, been trying to understand that better.
I 've been thinking why it is so difficult to understand these notions, and came to the conclusion that the problem is not only due to our experiences, the problem is also verbal. There are no words to describe situations that fall away from our experiences and senses, which is exactly what relativity theory is doing. OR ARE THERE? Plato (and Freud in is own words) say that simple statements (words) require deep understanding. I understood what the narrator is trying to commune when I realised that all objects near a big mass (like earth) have the same ANGULAR SPEED (two words) on the space time diagram. These two words crystalized the meaning of the theory and helped me remember all the details effortless.
I have a question pls At 6:10 you state that any forward motion in time is converted into downward motion in space.. thus motion *through space begins I saw another video which stated that although geodesic path in curved space-time gives us a path the body will take if it moves *through space, it does not explain how the motion *through space begins (if body was already in motion *through space, it would follow that path and fall to earth). It further explained the only reason motion *through space BEGINS is due to everything already being in motion *through space (the entire universe) and thats the reason they fall.. curved spacetime gives a path, but the motion *through spacewas already there before.. passage through time does not intitate motion *through space. Could u please explain what is right and why?
The videos is by 'But why' channel named 'what is gravity' Btw this was excellent video.. far better than the videos by bigger channels you mentioned. thank you ❤️
Hi Rajinder, thanks for this question and your kind remarks. There's some ambiguity here when we talk about motion; you could either mean "motion through space", "motion through time", or "motion through spacetime". When you say "although geodesic path in curved space-time gives us a path the body will take if it moves, it does not explain how the motion begins" or "the only reason motion BEGINS..." you're talking about motion through space. A critical concept here is to understand that for masses, there's only ever motion through spacetime (and never just motion through space or just motion through time). So it is the case that everything (the entire Universe of masses) is already in motion, moving at the speed of light through spacetime. (Here's a good article that explains this point a bit: medium.com/predict/we-all-travel-through-spacetime-at-the-speed-of-light-d60cb389dfc2). Nonetheless, if we clarify which type of motion (motion through time or motion through space), we can still speak of them as separate to clarify our discussion. It's important to understand that passage through time in the examples given in my video DOES initiate motion in space, in a sense. If you drop an object on Earth, it begins to accelerate along its geodesic specifically because it was situated in a region of spacetime where it travels faster through time than it had enough energy to sustain on its own (absent your hand holding the thing up). The "spacetime friction" this exerts on the object forces it to move along its geodesic once the outside force of your hand is removed. I hope this helps, let me know if you have any other questions.
@@IdeaListEye That was a great article and thanks for the explanation, it cleared up a few things. I've tried correcting my original comment to remove the ambiguity. So will it be correct to say the geodesic in space, geodesic in time and geodesic in space time mean one and the same thing(path)? Does it make any sense? And in curved space-time if any object is in motion through time it will move along its geodesic through time which inevitably also will make the object move along its geodesic through space (since they're same, but it has to give up some of its motion through time to achieve some motion through space, like MOI, angular velocity and angular momentum relationship) and it just so happens (due to nature of spacetime curvature) that the geodesic in curved spacetime is directed towards the mass in spatial co-ordinates which is causing the curving of space-time. Could you pls tell if this understanding is correct and refine if something's wrong Also how does time dilation causes motion through space? Like the example that top of apple goes through time faster than the bottom of Apple thus causing it to spin in some way (thats what was represented in other videos you stated) and that makes it moves through space.. Wouldn't the top part of apple just rot faster than the bottom and that would be it? No motion through space warranted
@@RAHISTILLL "So will it be correct to say the geodesic in space, geodesic in time and geodesic in space time mean one and the same thing(path)?" This is a confusing point: there's just the geodesic in spacetime, and it's made up of a space component and a time component (and to add to the confusion, the space and time components will be weighted differently depending on who's observing the object in question). Remember that geodesic just means "shortest path", and in this context it reflects the fact that it takes extra energy to travel anywhere other than along the current geodesic. Also, a geodesic is momentum-dependent; the satellites orbiting Earth are on geodesics that take them around in loops due to their angular momentum; if they didn't have that momentum, they would plummet to the Earth. I wonder if this video might clarify: ruclips.net/video/AwhKZ3fd9JA/видео.html "Also how does time dilation causes motion through space? Like the example that top of apple goes through time faster than the bottom of Apple thus causing it to spin in some way (thats what was represented in other videos you stated) and that makes it moves through space.. Wouldn't the top part of apple just rot faster than the bottom and that would be it? No motion through space warranted" This question demonstrates that my video was unable to convey this concept (understandable since it's a difficult concept!), so I'll try to describe it differently here. I'm going to borrow from another reply I made to another commenter; let me know if this helps! We need to build an understanding of how spacetime works, and to do so let’s start with special relativity, the version of Einstein’s theory that doesn’t involve gravitational fields. I’ll speak of space and time separately, but it’s always the case that these two are describing part of one thing, spacetime (similar to how I can talk about up/down and left/right in space as separate things, though it’s understood they’re forever and always part of the same thing, space). Imagine a Universe that is entirely empty of all matter except for two clocks floating in space and moving forward through time. All masses move forward through time by default, and these clocks have never been given a push, so they’re both sitting perfectly still in space. (As a brief aside, what does it mean to move forward through time, anyway? It means that the clocks are changing according to causal interactions laid out by the laws of physics; their atoms are vibrating, their electrons are oscillating in their orbitals, their quarks are quarking about in their protons and neutrons: a dense, dizzying frenzy of natural cause and effect interactions. At a larger scale, these interactions drive current through the clock’s battery, and larger still they actuate the ticking of the clocks through the tension and release of springs and the turning of gears (Incidentally, these interactions are mediated by the exchange of photons, packets of light, which travel at maximum speed through space and zero speed through time, which suggests a deep relationship between mass and spacetime and hints at why masses warp spacetime to begin with, but that’s a different story)). A mass that’s sitting perfectly still in space moves through time at maximum speed. These clocks then are ticking as fast as they’ll ever tick, and are accurately recording their speed through time as they do so. Now imagine one of the clocks has a rocket attached to it, and it’s ignited, sending that clock faster and faster in one of the spatial directions. Special relativity reveals (and you might need to do some googling here to understand why) that objects that move faster through space necessarily move slower through time. This is the nature of spacetime; you must exchange some of your speed through time if you want to move faster through space; these speeds are interconvertible. As that clock speeds up closer and closer to the speed of light through space, that clock ticks slower and slower relative to the still clock; it truly is moving more slowly through time. Ok, so the point here is that spacetime is a peculiar sort of currency exchange for any mass’s rate of change in the Universe; if that object has put all its “motion currency” into moving through time, that object must be motionless in space, and on the other hand if that object has put all its “motion currency” into moving through space, that object must be motionless in time (and must actually be made of light and nothing else, moving at the speed of light through space). It might not seem like it, but this relates back to your original question, “why the force of (gravitational-seeming) attraction due to time dilation?”. The way that masses like the Earth warp spacetime is peculiar: they make it so objects farther away from the mass automatically have more of their “motion currency” converted to motion through time, and objects closer to the mass automatically have more of their “motion currency” converted to motion through space (towards that mass). That’s what “warped spacetime” means: it’s referring to how much of this peculiar exchange rate is favored towards motion through time and how much of it is favored towards motion through space at any point in space. Far away from any masses way out in space, spacetime is more or less “flat”, meaning the exchange rate gives maximum pace through time, miminum pace through space. (This doesn’t mean that objects slow down through space if they enter a region like this with a given velocity, just that they won’t be sped up further by any gravitational-seeming attraction). This peculiar warping is why clocks farther from the Earth’s surface tick faster, they’re moving faster through time due to the natural exchange rate offered by the warped spacetime. Note that this isn’t a direct interaction between the Earth and whatever happens to be nearby the Earth. Instead, the Earth interacts with spacetime in its vicinity, and its influence on spacetime in turn affects whatever objects happen to be nearby. This was a long way to go to get to the punchline: the gravitational-seeming attraction arises because in the absence of any other force, objects in the region of spacetime warped by the Earth’s mass have to accept its “motion currency” exchange rate, their interaction with spacetime dictates it. Objects without an extra energy source must accept the “cheapest motion currency” available, which coincides with traveling along a geodesic in spacetime. Near the Earth, this means giving up faster motion in time for faster motion in space towards the Earth’s center of mass. This is because, for example, sitting on the surface of the Earth requires you to move faster in time than your “motion currency” can pay for; your body alone only has the energy to fall straight downwards in space and ever slower through time rather than travel forward in time at the rate that you are (it’s a shorter path through spacetime to fall straight downward into regions of spacetime where time moves more slowly; it’s literally a less energy-intensive direction through spacetime to go). You can only remain on the surface of the Earth because the floor provides the force to hold you up in this faster time domain. The pull you feel downwards is your mass ever trying to accept spacetime’s exchange rate and speed up downwards, slowing down through time.
@@IdeaListEye That was a very thorough explanation (although I had read it before in the comment you mentioned, it was good revision regardless). Thank you. Sry, I think framed that question rather poorly.. of course i understand why time dilation causes sensation of gravity (i think). What i meant to ask was in those videos (science asylum and PSB) they have this animation that shows the side of object away from the mass( let's say earth) Torquing in towards earth making the object rotate around it centre of gravity which makes it fall towards earth. I dont quite understand how does that rotation around the axis fit into the explanation that you presented here. Could you please explain that? Also i think i understand when you say there are no geodesic in space or time individually, but through space time. Its just very weird to visualise.. would it be correct to say that "passage of time has a preferred path in the physical 3 dimension"
You attempted to be clear and intuitive in detail at both your space and our time, the graph puzzle links a solution, IF those historical theories where snapped together as one. Allowing a healthy questioning, without any rightous declared says. We don't get much *mass* explanations, from those other channels you mentioned on this one.
Interesting hypothesis about inertia. Why do you think the bending of spacetime would resist acceleration but not constant motion? Do you know of any analogy for such a thing in known physics?
Bending of spacetime resists acceleration, not velocity. I think this is because of time. All objects must move in time and/or space. Increases in velocity is converting relative time velocity into space velocity. At the speed of light, time does not pass in your reference frame. Put another way, one might say that inertia or velocity is caused by the passage of time. More fundamentally, the constant speed of causality causes inertia.
@@bminerrolltide I realize that that's the common understanding based on the idea that everything travels at c through spacetime (which is perhaps equivalent to saying that c is the constant speed of causality, as you say). But he's trying to go deeper than that and explain exactly why spacetime resists acceleration, so I'm asking him to complete that explanation to account for the lack of resistance to constant velocity, if that makes sense. If you have any ideas, lmk.
@@GumbyTheGreen1 yeah I think I understand what you're saying. I think bending of spacetime does in fact resist any change in position, but this resistance is balanced by the object's inertia, which is caused by "the constant passage of time." Haha sounds kinda weird to say. Put another way, as the object passes through space, spacetime bending follows the object because time is passing at the same rate as the object's velocity through space. Or put another way, the object is moving on its geodesic.
This is kind of why you can say that "time" causes gravity. More precisely you can say that gravity is caused by all objects moving through spacetime at c. The mass bends spacetime, and its constant velocity in spacetime causes spacetime bending to follow the object in space. Thus, other nearby objects are pulled along these bends in spacetime, as well (gravity).
Hey Gumby, great question! I'm glad someone asked this. First off, I should state clearly that this is purely an intuitive description and understanding (in other words I don't have a derivation for this effect, but it makes sense to me (so it should of course be taken with a grain of salt)). In my view, constant motion is a case of "balanced" spacetime warping. In other words. as the object approaches spacetime in the forward direction (really, it should be ok to talk just about space in this case, since that's the relevant dimension, but I'll stick with spacetime), the spacetime's attractive influence on that object helps propel it forward. On the flip side, as the object recedes from spacetime in the backward direction, the spacetime's attractive influence on that object resists its forward motion. I see these two influences as balancing perfectly, leading to the observation summed up by Newton's first law (A body continues at rest or in motion in a straight line with a constant speed until acted on by an unbalanced force). In the case of an acceleration, to understand my perspective, look at it like this: the unbalanced force on the object is asking approaching spacetime and receding spacetime to warp at a different rate, upsetting the balance described above. For example, adding speed to the object in the direction it's already traveling requires spacetime to warp in the forward direction and unwarp in the reverse direction more rapidly, which takes energy to do (related to the inherent "stiffness" of spacetime ultimately defined by the permittivity and the permeability of spacetime). That energy is now considered part of the object's kinetic energy, but it's really contained in its modified relationship with spacetime (warping/unwarping spacetime more rapidly in its direction of motion).
Hi! But why does the body choose the "shortest path" between the white lines? Does it have to do with minimizing the action (the length of the world line)?
Hi! Yes, as with all spontaneous actions in physics, it's a result of the system seeking the lowest energy state. Masses follow local geodesics because it requires the least amount of energy (i.e. the object would require extra energy to follow any of the non-geodesic paths; for example, a satellite in orbit is only able to maintain orbit because it has a lot of kinetic energy perpendicular to the geodesic provided by the Earth's mass).
I realize for the sake of explaining the principle of geodisks in space-time you have used a skyscraper extending to outer space and exaggerated the time dilation enormously between the bottom & top floors. But for an object on earth such as an apple the time difference between the top of the apple and the bottom of the apple is in nanoseconds or less. How does such a miniscule time difference translate to such a high acceleration due to gravity of 9.8m/sec^2 for the apple?
Hi Ravi, good question, and good observation (I should've made it more clear in the video that this was an extreme exaggeration, as you pointed out). It turns out that in this context, 9.8m/sec^2 is quite a modest acceleration. This is because it must be considered relative to the speed of light, 300km/sec; all objects at rest are considered as moving at the speed of light in time, and when they begin to accelerate relative to other objects, the accelerating object trades some of its speed through time for speed through space (i.e. it slows down in its motion through time). From this perspective, only a very small fraction of an object falling on Earth's speed through spacetime has been converted from the time dimension into the space dimension. Here's a great video on this point: ruclips.net/video/au0QJYISe4c/видео.html
The latter; it's not possible to find a place where there is no gravity, because gravitational influences propagate at the speed of light, and if a place is findable to us, it's only because that thing is within the observable Universe (where light can have traveled to us since the big bang). Let's say you think you found a place where there is no gravity, somewhere far out in space as distant from any stars or dust clouds as possible. The fact that you can observe that place shows that that place is affected by the Earth's gravitation (because gravitation propagates at the speed of light, and you can only have observed that place if you can look at light coming from that place and its vicinity). There would have to be exactly the same mass density in every direction from any point for 13.7 billion light years in order for that place to have perfectly balanced gravity, and then if you wait a microsecond, everything in the Universe has slightly shifted position relative to that point, and it's essentially impossible for the mass balance to stay the same over that duration. So, even though astronauts float when, e.g., in transit to the moon, they are still very much influenced by the Earth's, the Sun's, the Moon's, and the Milky Way's gravity.
@@IdeaListEye A typical hypothetical example of no gravitational field is intergalactic space. How fast would a clock tick there as compared to here on Earth, within the solar system and so on?
@@IdeaListEye Obviously a clock ticks faster as it is moved farther from the earth, and presumably still faster if out the distance of, say, Neptune, as it is farther from the sun, and so on. I guess what I am getting at is, how much faster could the clock tick?
@@comic4relief Basically, yes, there's always time dilation. Wherever masses interact with spacetime (an interaction that propagates through space at the speed of light), there is time dilation. The magnitude of that time dilation varies drastically from place to place in space, from almost 0 way out in space far from any masses, to almost infinity near the surface of a black hole. So even in your hypothetical example of intergalactic space, that's not a "no gravitational field" case, it's an "infinitesimally small gravitational field" case; it's overwhelmingly likely that the gravitational gradient is nonzero everywhere in space. A clock out in intergalactic space would tick about 1 nanosecond faster per second, so obviously the effect is quite small (it would take a billion Earth seconds for the clock out in intergalactic space to tick a billion and one seconds): hyperphysics.phy-astr.gsu.edu/hbase/Relativ/gratim.html#c4 This is of course assuming that clock is at rest relative to the Earth; if it's in motion relative to the Earth, that would result in kinetic time dilation that would change the result.
Just 86k views?? This video deserves to be one of the best science videos I've ever seen, so much information in such a short time, and very well and easily explained as well. You are great sir. One request for u, please explain delayed choice and delayed choice quantum eraser and other quantum related ideas sir since you'll be able to explain them simply as well I'm sure 🙂❤️❤️❤️
Sabine Hossenfelder did a great video on the subject recently. Basically, you need to combine the interference pattern from both detectors when interpreting the result. You can’t just show the pattern from one detector which a lot of other videos do.
Wow, thanks, Umer! Very kind of you to say. I'd like to dig into those topics, thanks for the request. I have been reading about quantum computing recently, and it's monumentally complicated and confusing-- it might be a long time before I have anything valuable to say, but stay tuned!
"Why does mass warp spacetime?" The simple answer to the question is: relative parallax causes infinitesimal particles moving at instantaneous velocities to "slow down" or "warp" in space. That may sound impossible, but read on. It solves a LOT of problems and makes more sense than any of the current speculations. I have been working on this for a long time and finally figured out very recently that infinitesimal particles (no size) create mass because of a parallax effect as they pass each other in space. The particles "register" each other as moving at slower rates than themselves. The further away the other particle, the slower it appears to move. This is exactly the same effect as two airplanes who think they are flying parallel, but within a few seconds, they quickly discover that they were on a collision course, but too late, they collide. Now these infinitesimals can never collide (being infinitesimal), but as they pass the same point in space, each becomes attracted to the other because to both particles, their paths curve, even though neither has changed course. This relative curvature causes the particles to seek a straight line in relation to each other, forcing their paths through space to curve. As their paths diverge, they become locked by a gravitational pull as each slows down in relation to the other, shaping their path as a curve. This creates a sine wave. Time itself emerges from the relative movement of infinitesimal particles. The particles are normally inclined to change in position without change in time (instantaneous movement through space), which is identical in appearance to a stationary particle that changes its time without changes in space (instantaneous movement through time). However, the particle moving through space instantaneously has a pathway, even though it does not trace out that pathway in time. The above-mentioned curvature occurs as two particles' paths cross in close priximity relative to the rest of the universe. But since they register a velocity of each other as slower, due to a hierarchical relationship to all other particles in the universe, their path curves together, warping space time, and both particles are slowed through spacetime, though both particles are technically moving at instantaneous velocity. This is what I call relative parallax. Their angle in relation to each other creates a spiral wave we register as a sine wave. Any other particles in close proximity can alter the path of the first particle pair and so on, causing a change in frequency. (I believe these pairs are photons or that photons are pairs of pairs of these particles based on recent findings at the LHC and the mathematical model of a photon having two parts revealed in December, explaining their spin 1), and I am currently of the opinion that the more parallel the particles travel, the flatter the wave, while the more perpendicular they travel, the more trophs in the wave, based on how much energy is transferred by the other particles. However, I am willing to accept the opposite. I still have to model it properly. I had found that the particles have to start out with a rest velocity of instantaneous movement, leading to causing time, spacial curvature, energy and all four forces. That does not happen with non-moving particles starting with instantaneous time. In that scenario energy has to be added, but in my scenario, time, energy, mass and gravity emerge naturally. It also satisfactorilly shows that the universe is classically deterministic without some underlying, inexplicable, spooky "quantumness". (Though this does not necessarily mean that consciousness is superdeterministic, as the parts can exceed the whole to allow conscious agency.) QM is still just probability based on group theory, not a fundamental quality of space. Bound photons sharing and trading infinitesimals creates electromagnetism and other particles in effectively three-body systems, producing 1/2 spin. It is the destabilization of the gravitational monopoles of the bound infinitesimal particles that creates electromagnetism. The restabilization of the field with additional particles having a counter-stabilizing effect produces weak force, and the perfection of this balance produces the strong force.
So this is the way to think about uniting the forces into one grand theory. So simple and elegant. Just as scientists envisioned since the Greeks. Bravo!
Hi Ildar, great question. This all comes down to the equivalence principle view of gravity, how an object held stationary in a gravitational field (like the apple on the branch) is equivalent to that same object accerelating in a rocket far out in space away from significant gravitational fields. If these two really are equivalent, then they are amenable to equivalent descriptions in terms of energy. For an apple accelerating far out in space, it’s clear how much energy it takes to accelerate at g for one second, it’s the apple’s kinetic energy after that second (1/2 * apple mass * g^2). The energy is delivered by the rocket’s propulsion, and the store of energy is spent by that propulsion. How about the apple on the branch? In the equivalence principle view, the branch is accelerating the apple upward at g just like the rocket’s engines (and the tree is being accelerated upward by the surface of the Earth), so the same amount of energy is needed, and it’s delivered through molecular bonds in the branch. The question of what store of energy is being depleted is more difficult. I think a more general way to ask this question is “what energy is being converted into the apple’s kinetic energy?”. In a roundabout way, it’s the interaction of mass with spacetime that supplies this energy (similar to how it’s this interaction that supplies an object in a gravitational field’s potential energy in a classical framework). The Earth’s mass interacts with spacetime to warp it at a global level, and it’s this warping that causes the apple’s geodesic to bend towards the center of the Earth. I agree with your stance (what I think your stance is) that this equivalence principle version of events is highly nonintuitive, especially when you consider it from the standpoint of the conservation of energy. This discussion that someone shared with me regarding this video might help clarify the situation, especially Viktor Toth’s answer: qr.ae/pGqeZl
Thanks for creating and posting this awesome video! I could never understand why an object released from a stationary position (like a tree branch) in a gravitational field would start moving if there is no force involved. What would give it the impetus to start moving? Now that I've seen your two-dimensional graph of warped space-time, I finally think I understand it. If I understand this correctly, the object is fixed on a geodesic position, but the geodesic fabric is changing with respect to time, thus causing the object to move through the space dimension. i hope that's more or less correct anyway.
Hey David, you're welcome! Glad it helped you out. Re. "If I understand this correctly, the object is fixed on a geodesic position, but the geodesic fabric is changing with respect to time, thus causing the object to move through the space dimension." I think that is more or less correct, but a better way to think about it would be to say that the object is fixed on a geodesic path, not position, because every object is always traveling through spacetime; there's no fixed position because even if it's somehow perfectly stationary in space, the object is still traveling forward through time. Using the apple as an example, the geodesic path the apple seeks to take (its path of least energy through spacetime) has it traveling downwards due to the curvature of spacetime making every other path require more energy. It's only kept from following that path by the branch exerting a force on it away from that path (upwards). So, to be clear, it's not that the "geodesic fabric is changing with respect to time"; that geodesic is fixed by the interaction between the Earth's mass, the apple's mass, and spacetime. When attached to the branch, at every instant the apple is traveling further through spacetime than it would if it could follow its preferred downwards path because the branch is pulling it away from that path into a region where time passes more quickly (causing the apple to travel through more time than it would if it were in free fall along its geodesic). I hope that helps! Let me know if you have any questions.
@@IdeaListEye Thanks for clarifying that. I see what you mean by the object not being "fixed" on the geodesic. It is always moving through time. I hope I've got that correct now. I also think I see what you mean when you say the geodesic is fixed, not the object.
Thanks! I'd like to add that the visualization at 10:43 is by the channel ScienceClic, I neglected to include a credit there (my bad!). (Their channel is superb)
Great video, thank you... just a question though... according to equivalence principle, an object in free fall is like a floating object moving freely through its geodesic in spacetime (like the space station)... so according to my understanding, time for the falling apple should be as fast as it is for the space station until it falls on earth, at which its time will move slower... am I missing something?
I loved your description of the attraction of matter to space-time causing gravity.😀😍 Resistance to movement change from forces and gravity and geodesics. The graphic was good to imagine matter sucking in space time. It helps give an intuition for it. Your questions give us ways to think about it and your answers frame it well, for sure! (Why does it take energy to move an object from its geodesic, ie an asteroid in space.)
Thanks for this video. With such a grip on spacetime and matter/energy, you should take the next step into fleshing out how entropy and enthalpy further quantize the events of causality. Essentially, what I’m asking you to do is to connect relativistic mechanics to quantum mechanics via focusing on entropy/enthalpy and how they define the arrow of time (or as I put it, further quantize causality). Neither the standard model nor relativity make enough sense to fully model the world without each other, which is why Einstein spent most his life seeking the bridge and it remains the holy grail of physics. From what I understand about relativity, to consider gravity/time a force mediated by spin-2 tensor bosons is… unintuitive, while to a particle physicist, it is intuitive to consider gravity/time a fundamental force mediated by force carrier particles, as included in most standard models. It’s literally looking for a fundamental particle for time, which imo is like looking for fundamental force carriers for speed, momentum, or inertia. These all seem like composite, non-fundamental forces for which there wouldn’t be a bosonic force carrier. It seems to me like we already have all the fundamental particles we need, what we are missing is a better understanding of how they interact via enthalpy and realize entropy. That’s so far quantifiable via high level quantum mechanics that can model up to a sufficiently composite, classical degree. Furthermore, I would interested to see if the right understanding of the connection between quantum mechanics and relativity via entropy/enthalpy could also shed a bright light on dark matter and more importantly dark energy. Cheers, pls do this for me even if you manage to prove this all wrong
Hey JackBlackNinja, thanks for this suggestion. It's an interesting idea, but I'm not particularly qualified to confirm or deny it. I'd encourage you to flesh it out, and perhaps even make a video on your own to explore and express your idea! If you were interested in doing so and had questions, I'd be happy to help in that regard (re. video production, etc.).
@@IdeaListEye I would so much like to make a video myself but I feel like I don't have the physics prowess nor editing skills to pull it off. You did so well with this video, which itself deals with time, so was just thinkin you might be able to explore the so-called 'arrow of time' described by the 2nd law of thermodynamics, which is a macro composite of quantum phenomena called micro states. This connection between the arrow of time described by the quantum mechanics via the 2nd law and the gravity-time described by relativity seems interesting to explore. Anyway, I totally understand if it's out of your wheel house, it's certainly out of mine too! Keep up the stellar work boss
I was told many years ago that time closer to the centre of Earth runs faster , on the top of a mountain time runs slower . There are 5 levels or aspects of time .
I don't get one thing. You said it takes supplying energy, to move away from the geodesic. Like the apple hanging onto the tree. I also understand that according to the equivalence principle, the apple is being accelerated upwards. Both these explanations, that suggest that energy is being supplied, make me ask... where is that energy coming from? The branch can technically hold the apple forever. So how can energy just be created like this? Where is the energy being lost, to give the energy needed to hold up the apple?
Really great question, I appreciate that you’re digging into the most conceptually confusing (and potentially, challenging to the theory) point of it. Let’s think first about the classical version of this situation. In this view, the apple has gravitational potential energy (mgh) due to its position relative to the surface of the Earth, and zero kinetic energy. If the apple falls, its potential energy is converted into kinetic energy as it accelerates downward, until it hits the ground with potential energy 0, and its kinetic energy is dissipated via heat. Now let’s think about it from the equivalence principled “apple continuously accelerating upward” view. Here, the apple has zero gravitational potential energy (since we’re considering it as in a rocket ship out in space, away from significant gravitational effects), and the branch is accelerating it at g. Already there’s something suspicious about this setup; what if we wait for a year? Accelerating at g (9.8 m/s^2) for a year (31,536,000 seconds) would take the apple to 309,052,800 m/s, which is faster than the speed of light. This can’t be right. This article (en.wikipedia.org/wiki/Equivalence_principle#Einstein's_statement_of_the_equality_of_inertial_and_gravitational_mass) clarifies that the equivalence principle only holds when the volume of the experiment is small enough that tidal effects and things like exceeding the speed of light can’t be observed. So the right way to look at this might be to consider the apple just over the course of one second, right after the apple breaks free of the branch. Let’s say the apple was hanging 9.8 meters above the floor of the rocket. Here, the apple’s kinetic energy in the frame starts out at 0, and it has no gravitational potential energy; only the surrounding situation involves an exchange of energy (that is, the apple’s entire environment is accelerating). From the apple’s point of view, it’s sitting still while the floor of the rocket rushes up towards it at g, and the energy of the apple is only affected when the floor collides with it. Now if we look back at the situation on the surface of the Earth from the equivalence principle perspective, we can hopefully see more clearly what’s going on. The “gravitational potential energy” we would classically consider the apple to have has disappeared; we just have a perfectly stationary apple in an accelerating frame. The kinetic energy we also would classically ascribe to the apple after it breaks from the branch has also disappeared; again the apple is perfectly stationary, whereas the tree and ground accelerate upwards. There’s no energy exchange with the apple until the ground hits it. Ultimately, in switching between the two pictures, we’re switching between two ways of handling energy, and it’s much more intuitive (and therefore useful) to use the classical picture and its way of tallying energy. This doesn’t mean the “accelerating frame” picture is useless, just that it isn’t helpful when modeling things in a gravitational field. To dig in a bit further, let’s look at the rocket scenario a little closer. What is the rocket accelerating with respect to, and what is the “falling” apple stationary with respect to? The answer is spacetime. How about the surface of the Earth from the equivalence principle perspective? What is the surface of the Earth and tree accelerating with respect to, and what is the “falling” apple stationary with respect to? Again, the answer is spacetime. In both cases, energy is causing an acceleration of masses with respect to spacetime (in the former, that energy is in the form of rocket fuel burning, and in the latter, that energy is in the form of mass, that of the Earth in particular). What’s confusing here is that the rocket’s energy is being “spent”, whereas the energy of the Earth’s mass pulling in spacetime seems not to be. The energy comes from the Earth's mass's effect on spacetime (mass being equivalent to energy), and it accompanies all masses; in fact, that's where gravitation comes from in the first place, a conversion of energy from other forms into the form of mass warping spacetime. The gravitational potential energy between any two objects is due to their relative distances and the fact that bringing them closer together lowers that potential energy (and converts it to kinetic energy). The energy was "spent" in warping spacetime when that mass was formed, setting up this potential energy, (almost the same as stretching a spring between all masses everywhere).
FYI... Dialekt's channel and his series of videos debunks time dilation as the cause of gravity. He calls out PBS, Nick Lucid, Eugene, Sabine et al as all being incorrect. Who is correct I don't know.
I wonder if the warping of spacetime is a measure of interactions, a convergent phenomena where time dilation is relative to the number of particle interactions. E=mc² shows a higher energy system has greater mass, but from an information science perspective, a higher energy system means higher concentration of interactions, not necessarily higher energy interactions. "Time takes longer wherever more things are happening" kinda makes intuitive sense, and I see the flow of gravitation like air flowing from below a single spot in the desert; the sand is spacetime, and objects near it will tend to fall into the loose quicksand because it's shifting. I wonder if mass energy falling away from other mass energy light years away might cause dark energy, as gravity can't overcome other forces, the sum of all falling in one galaxy pulls at the spacetime between it and all others, like two quicksand pits pushing sand between them when an object falls inside.
This is an interesting brainstorm. I'm not sure how to "confirm or deny" this, but maybe an openminded theoretical physicist will chime in here at some point.
It is funny that you think the purpose of the video is to simplify what others failed to explain regarding spacetime. 😋u actually made it even harder to understand😘
Thank you so much for this. I was screaming at the screen while viewing the other videos you mentioned because of their darn time-flow vector that didn't seem to have anything do with spacetime (or just space). If felt like a relativistic three-card monte. So well done. But you've given me something new that just feels wrong (not saying it is, I'm just having trouble accepting it): If it takes extra energy to warp spacetime to get the asteroid to move over, (and this makes perfect sense), once it's up to speed it will keep going with no new energy added (at least no new external energy). But the asteroid is still warping spacetime anew as it moves along. That feels like this warping and unwarping should need energy too, just like it did to get the asteroid out of the well it had formed at rest. Or at the very least, the motion would run down as energy gets used up, and of course this doesn't happen. The direction of travel length contraction item seemed a little shoe horned in there (bare with me here, this is not meant as a critique). So I wondered if the length contraction has something to do with the asteroid being "attracted" to the spacetime it is about to move into and warp, and I just missed that connection. Or is there a length contraction gradient which would translate to a mass gradient would translate to a time gradient and we're back to what causes gravity but this time, in direction of travel; once an object is moving, or once spacetime is unwarping, does the object create its own "straight" geodesic? That the asteroid is "attracted" to the spacetime it is about to move into (in this example), feels similar to why mass (or probably better: energy) causes a dent in spacetime. I'm hoping the answer is not "because it does" as it currently is for why mass dents spacetime. It also feels a little like something riding a wave. The displaced spacetime behind pushes the asteroid forward - but there is an equal ridge of spacetime in front that must be overcome, so the energy supplied to ride down the hill would be the same as the energy to climb the hill in front. (unless due to motion there is now a time gradient so there is a lag between when the energy is supplied and needed.) Or is it that spacetime itself has inertia? Again, thank you, I've been chasing the "time causes gravity" for some time now and the veil has been lifted.
Thanks! And thank you for these insightful comments, I was hoping someone would raise some of these issues. "If it takes extra energy to warp spacetime to get the asteroid to move over, (and this makes perfect sense), once it's up to speed it will keep going with no new energy added (at least no new external energy). But the asteroid is still warping spacetime anew as it moves along. That feels like this warping and unwarping should need energy too, just like it did to get the asteroid out of the well it had formed at rest." This is a great question. To clarify the picture, it's better to say that it takes extra energy to change the rate at which the asteroid warps spacetime, not just that it takes energy to warp spacetime. When you speed up the asteroid in the x direction, the asteroid now needs to warp more space per time in the forward x direction, and unwarp more space per time in the backwards x direction. Because mass is attracted to spacetime, the object moving through more spacetime in the x direction is more strongly attracted to spacetime in the x direction. By the same token, the object moving away from more spacetime in the backwards x direction is more strongly attracted to spacetime in the backwards x direction; the influence of the extra warping in the forward x direction and the extra unwarping in the backwards x direction cancel out, leading to a constant velocity. This is the case in any inertial frame (even for a hypothetical object that's completely still in space), the object's attraction to spacetime in every direction cancels out, leaving the object moving at a constant velocity. It takes extra energy to upset this equilibrium by causing the object to warp/unwarp extra spacetime in any direction (which results in that object picking up velocity in that direction). One way to say this would be that the extra attraction that the mass gains to the more rapidly approaching spacetime in the forward direction is "paid for" by an extra "drag" on the mass by the more rapidly receding spacetime (which is also attracted to and attracts the mass) in the reverse direction. I like your idea of an object moving through spacetime as similar to something riding a wave, but I disagree with the way you have it stated ("The displaced spacetime behind pushes the asteroid forward - but there is an equal ridge of spacetime in front that must be overcome, so the energy supplied to ride down the hill would be the same as the energy to climb the hill in front."). Try to imagine this wave instead like an attractive field, maybe like a magnetic field. The approaching spacetime attracts the object forward, and the receding spacetime attracts the object backwards, and the two cancel out (for any constant velocity in the absence of other forces). The thing that applying a forward force does is cause the object to be attracted to more spacetime in both the forward and backward directions per time (and thereby to travel more distance in the forward direction per time). You're right that the bit about length contraction was a bit shoehorned in; I included it in the video because length contraction and time dilation are correlated with increased velocity through spacetime, but not because that fact gives useful explanatory value in the case we're discussing. The space contraction and time dilation that occurs for objects moving relatively faster than others can be understood better in the context of light clocks (I'll assume you're familiar, let me know if you'd like any clarification). For a light clock traveling through space faster relative to another light clock, the photons must travel farther to tick off the same amount of time (resulting in time dilation), and space also contracts in the direction of motion to accommodate this effect. This is true not just for clocks, but for all physics: in order for the equivalence principle to hold, for an experimenter traveling at 99% the speed of light, the photons involved in the electrical currents in the experimenter's neurons, in the biochemical reactions keeping them alive, and in lighting their experiments would need to travel a ludicrously long distance in the forward direction if space contraction in that direction didn't compensate (alongside time dilation). Kinetic time dilation and space contraction are required to allow objects moving near the speed of light experience the same laws of physics that objects moving at 0 speed follow.
@@IdeaListEye Thanks for the in depth response and for the respectful tone (so many of these presenters get down right nasty when you ask something) I'd like to solve time travel just to go back before they knew these ideas and give them a taste. There was always a time before we all knew. Anyway: The befuddlement around the inertia section comes from the warped spacetime resisting being unwarped and needing energy to do that. So far so good. But then one the unbalanced force is removed the asteroid continues to anger spacetime as it unwarps the space it is in and warps the space in front, and to my thinking, the asteroid would have to expend its kinetic energy to keep that up; the warpage acting kind of like friction. Why is a body in motion more slippery than a body at rest? (with respect to the spacetime it warps) Regarding mass's attractiveness to spacetime, based on the inflow 3D representation of this it seems like that flow would empty the universe in short order. Is this the correct way to think of it? Is this better than the idea that mass just warps spacetime instead making a sink? (so a still from that animation instead of a constant flow?) Is it a flow or a stretch? Assuming a spheroid asteroid of even mass distribution, time dilations would be consistent all the way round, spacetime warping would be the same all the way round, I'm having trouble understanding why spacetime would being willing to unwarp and warp in the direction of travel with no added energy since it took energy to to do it in the first place from rest. Or is it better to look at it this way: From a geodesic point of view, instead of saying it takes energy to unwarp the space, would it be better to say it takes energy to alter the geodesic? (I think you kind of said that) For the at-rest sphere, the geodesic is as you depicted. With a push, we are angling it's geodesic over a little bit (I think) where it stays once the push is removed. On this new geodesic it's free to continue on its merry way because that is the lowest possible energy state and it's warping spacetime as it goes because, well, that's what mass does inherently. (BTW, to be clear, it's not that I doubt this happens, it's the depiction that energy is required to unwarp and warp space anew that has me frowning) As you say, if inertia is still a shoulder-shrugger even for Kip Thorne et al then there may be no answer to this. Whether the sphere is warping spacetime while it moves or is stationary probably doesn't matter - the energy to do that is built into the mass of the object doing the warping. Does the motion really matter at all? Spacetime is reacting to the proximity of a bundle of energy and I"m not sure that needs any help or incurs an energy debt. I love your geodesics diagrams for time causing gravity. I have now found another video that finally visualizes time and length contractions and dilations by warping the graph grid itself with the lorentz tranforms, while the spacetime motion remains the same - light bulb moment! (I prefer to get the concept before digging into the math - I came form the shut up and calculate school - I get the right answers when doing the math but I'm queasy about why. I could be wrong on this but I think Einstein made bigger leaps in the field by conceptualizing than in doing the math) Yep savvy with light clocks. I was just thinking perhaps length contraction had something to do with how the object would be attracted to spacetime (bit of a hail mary on my part) and thought that's why that segment was there. Can't-get-puzzle-peice-to-fit!
@@markrichards5630 _"But then one the unbalanced force is removed the asteroid continues to anger spacetime as it unwarps the space it is in and warps the space in front, and to my thinking, the asteroid would have to expend its kinetic energy to keep that up; the warpage acting kind of like friction."_ The thing that "angers spacetime" (lol) is not the fact of the extra spacetime warping, it's a change to the _rate_ of spacetime warping. This is why an object way out in space resists acceleration proportional to its mass, but moves at a constant velocity (no matter how fast, up to the speed of light) in the absence of other forces. Spacetime warping at any _constant_ rate offers no resistance to motion (so it's wrong to think of it as like friction). The thing that is "frictional" is changing the _rate_ at which an object warps spacetime (which corresponds to changing the object's velocity through spacetime, i.e., accelerating it). Once you remove the unbalanced force, you're no longer changing the rate at which the object is warping spacetime, and the object/spacetime happily continue on in their new, faster interaction. _"Regarding mass's attractiveness to spacetime, based on the inflow 3D representation of this it seems like that flow would empty the universe in short order."_ I borrowed that video representation from a great youtube video, ruclips.net/video/wrwgIjBUYVc/видео.html. Be careful in your reading of it- it's an attempt to show both space _and_ time simultaneously, and it's not showing space warping as time passes; it's instead showing inertial spacetime frames (and is a bit of a confusing picture because of that). The warping of a mass at rest far out in space is constant, and the warping of time by that mass is also constant, so there's no inflow of spacetime. The inflow applies to other masses embedded in spacetime whose geodesics have been directed by the first mass's spacetime warp towards that first mass. _"Whether the sphere is warping spacetime while it moves or is stationary probably doesn't matter - the energy to do that is built into the mass of the object doing the warping. Does the motion really matter at all?"_ The motion definitely matters, and the nature of the sphere's warping of spacetime while it moves or is stationary _defines_ that sphere's motion (in particular, its momentum). If you believe in the conservation of momentum, the motion definitely matters. Specifically, the rate at which spacetime is warped by a moving mass (with that rate highest in its direction of motion) _is equivalent to_ that mass's momentum.
@@IdeaListEye Thanks for taking the time. This makes sense now - any disturbing of a motionless object or a constantly moving object would be an acceleration and therefor you can either look at it as that energy is needed to change the rate of motion or change the rate of warping. For my noggin I think I like the idea that the energy used to change the object's motion is in fact changing its geodesic. Is this a reasonable way to look at it? Ignoring relativistic speeds, is it safe to say that because the mass of the object doesn't change, the local shape of the curve it produces in spacetime doesn't change, and the geodesic just moves over, or, does the angle of the geodesic change too at the new constant speed? I love how spell check turns a mangled "geodesic" into "videodisc" - I guess that's the flat-earther solution to this problem)
@@markrichards5630 That's right, the energy used to change the object's motion is changing its geodesic. This is how satellites stay in orbit: by putting in the right momentum, they now travel along a geodesic more or less parallel to the surface of the Earth.
Inside an atomic clock an oscillator emits about 4GHz photon that reaches a Cesium atom, which absorbs and emits about 4G photon times per second. If I place a second atomic clock near a mass the Cesium atom emits 4G - a small value of photons per second. The mass influences what? The frequency of the photon of the oscillator? The oscillation frequency of Cesium? How ? By lengthening the space between the oscillator and the atom?
Great question! I'll be honest and say I don't know the exact details here (hopefully someone more informed can chime in), and add that the interaction of particles with gravity is poorly understood (see quantum gravity for more). In general, mass warps spacetime, so the change in the metric of spacetime is why the atomic clock ticks more slowly relative to unwarped spacetime. Does that help answer your question?
Thank you for pointing out that there is no generally agreed upon theory for why inertia exists. I have been trying to find the answer to that question for years and no one else has simply said that "we don't know". They always just talk around the subject. I have watched pbs space time, dr lemon, and many others. Arvin an gets closer than most, but only you have just come out and said it.
What struck me was that you can imagine it time dialation ( or time contraction) as moving up the slope of the time curve, i.e. gravity is the result of the slope of the change in time dialation.
Thanks, SpacetimeGrid! I was having a bit of a rough day, it's really nice to hear that kind feedback, just the pick-me-up I needed! Thanks also for your idea about a donation link, I had been thinking about making one for awhile and you gave me the push I needed. Here's the link, many thanks for your support! donorbox.org/idea-list-youtube-channel
Great question, this is a major point of confusion on this topic. The idea that "we are not attracted to the Earth but rather pushed up from it" comes from the "equivalence principle", a hypothesis dating back 1,500 years that guided Einstein's development of general relativity. Briefly, Einstein's equivalence principle holds that the mechanism for the force experienced by someone sitting on the surface of the Earth pulling them downward is indistinguishable from the mechanism for the force experienced by someone far out in space, accelerating at g. (This is similar to how, when you enter an elevator and start accelerating upward, you feel heavier while you're accelerating; in fact, if you stood on a scale, the scale would show you weighing more while you are accelerating upward). In this sense, there should be no difference between a framework in which the Earth is attracting you downwards at g versus a framework in which the Earth is accelerating you upwards at g. That's all well and good, but the first case is immediately intuitive to us, whereas the latter case seems ludicrous (e.g. the Earth would have to be ever expanding in every direction for this to be the case, etc.). What gives? I think the right way to look at this is that neither case is exactly true, because they aren't looking at the underlying mechanism, which is spacetime warping and your mass's interaction with that spacetime warping. So, the real story underlying both cases is that the Earth's mass interacting with spacetime warps spacetime (especially the time component of space), so that the forward direction in time for any mass has a component in the direction of the Earth's center of mass (in a sense, time is bent into the "downward" spatial dimension, and spacetime "flows" in that direction). Your mass also interacts with spacetime, and is "attached" to spacetime by that interaction. When spacetime flows towards the center of the Earth, you're attached to that flowing spacetime, and therefore your mass also is pulled along with that spacetime. The confusing part here is that the relevant "flow" occurs in the time dimension, (i.e. where should a mass go over time given the nature of spacetime in the vicinity?), because it's nonintuitive to picture a geometrical aspect of time. I think it's fair to think of it as: the time aspect of spacetime answers "what should happen next?", and in this case the time aspect of spacetime says "masses should move towards the Earth's center of mass" or more broadly, "masses should move in the direction of the 'deepest spacetime well nearby' with the most urgency", and time says this because of the way masses warp spacetime. I hope this helps, I'm not sure if it's more or less helpful written out like this.
@@IdeaListEye thanks so much for this clarification. My confusion now lies on why mass produces this effect in space-time. Thanks to you I start understanding the consequences instead. I will focus more on the equivalence principle possible interpretations.
@@alessioandreoli2145 Why does mass produce its effect on spacetime? Now that's a great question; turns out, no one knows why that is, really. The Higgs mechanism is something of an explanation, but that kicks the ball down the road to "why do massive particles interact with the Higgs field?", which I believe is unknown. Similarly, "why do electrons interact with the electromagnetic field?" is unknown: some things are known solely from our observations about them, and not due to a more fundamental theory from which we could predict those things.
Doesn’t the spaceship bring its own gravitational field which will have a significant influence on the asteroid since it’s the ONLY gravitational field in that region of space?
Good observation that the spaceship brings its own gravitational field. However, whether or not it's the _only_ gravitational field in that region of space doesn't change how significant its influence is, which is negligible. Imagine the gravitational attraction you feel towards a large plane as you're getting ready to board; it's completely impossible to notice, because gravity is such an incredibly weak force for smaller masses like this.
@@IdeaListEye But it’s not negligible . As the ‘only’ gravitational field in this region it has a huge effect. Your comparison with a large plane is irrelevant as that plane is competing with the Earth’s gravitational field which is absent here.
@@arnesaknussemm2427 The magnitude of the gravitational force between any two masses is independent of any other gravitational forces on them. At non-relatavistic speeds, it's Newton's universal law of gravitation, F = G*(m1*m2)/r^2. In other words, there's no such thing as gravitational fields "competing" with one another to reduce the force of another gravitational field.
@@IdeaListEye I know this but the EFFECTS of a gravitational field can be cancelled or reduced by another. The Apple only falls from the tree when the effects of the electromagnetic force hitherto holding it up are reduced ie the stalk breaks allowing the much weaker gravitational force which was always acting on it to have a greater effect.
The casimir effect is probably related to why mass warps spacetime, I tried making a very simple abstract model of it (probably terrible way to go about it) but it would make sense, an empty region of space exerts a certain amount of force, the force pushes equally on other empty space and it cancels out giving flat curvature, as soon as any mass occupies it, it "blocks out" the things the effect emerges from and the force is no longer fully balanced out on neighboring regions of spacetime. like there is something that props up spacetime so it is flat, like if you had a trampoline with the skin of it levitated by something that is "obsured" by mass
Hi Parker, great question. This all comes down to the equivalence principle view of gravity, how an object held stationary in a gravitational field (like the apple on the branch) is equivalent to that same object accerelating in a rocket far out in space away from significant gravitational fields. If these two really are equivalent, then they are amenable to equivalent descriptions in terms of energy. For an apple accelerating far out in space, it’s clear how much energy it takes to accelerate at g for one second, it’s the apple’s kinetic energy after that second (1/2 * apple mass * g^2). The energy is delivered by the rocket’s propulsion, and the store of energy is spent by that propulsion. How about the apple on the branch? In the equivalence principle view, the branch is accelerating the apple upward at g just like the rocket’s engines (and the tree is being accelerated upward by the surface of the Earth), so the same amount of energy is needed, and it’s delivered through molecular bonds in the branch. The question of what store of energy is being depleted is more difficult. I think a more general way to ask this question is “what energy is being converted into the apple’s kinetic energy?”. In a roundabout way, it’s the interaction of mass with spacetime that supplies this energy (similar to how it’s this interaction that supplies an object in a gravitational field’s potential energy in a classical framework). The Earth’s mass interacts with spacetime to warp it at a global level, and it’s this warping that causes the apple’s geodesic to bend towards the center of the Earth. I agree with your stance (what I think your stance is) that this equivalence principle version of events is highly nonintuitive, especially when you consider it from the standpoint of the conservation of energy. This discussion that someone shared with me regarding this video might help clarify the situation, especially Viktor Toth’s answer: qr.ae/pGqeZl Here’s also some more clarification from a similar question I was asked in another comment: The idea that "we are not attracted to the Earth but rather pushed up from it" comes from the "equivalence principle", a hypothesis dating back 1,500 years that guided Einstein's development of general relativity. Briefly, Einstein's equivalence principle holds that the mechanism for the force experienced by someone sitting on the surface of the Earth pulling them downward is indistinguishable from the mechanism for the force experienced by someone far out in space, accelerating at g. (This is similar to how, when you enter an elevator and start accelerating upward, you feel heavier while you're accelerating; in fact, if you stood on a scale, the scale would show you weighing more while you are accelerating upward). In this sense, there should be no difference between a framework in which the Earth is attracting you downwards at g versus a framework in which the Earth is accelerating you upwards at g. That's all well and good, but the first case is immediately intuitive to us, whereas the latter case seems ludicrous (e.g. the Earth would have to be ever expanding in every direction for this to be the case, etc.). What gives? I think the right way to look at this is that neither case is exactly true, because they aren't looking at the underlying mechanism, which is spacetime warping and your mass's interaction with that spacetime warping. So, the real story underlying both cases is that the Earth's mass interacting with spacetime warps spacetime (especially the time component of space), so that the forward direction in time for any mass has a component in the direction of the Earth's center of mass (in a sense, time is bent into the "downward" spatial dimension, and spacetime "flows" in that direction). Your mass also interacts with spacetime, and is "attached" to spacetime by that interaction. When spacetime flows towards the center of the Earth, you're attached to that flowing spacetime, and therefore your mass also is pulled along with that spacetime. The confusing part here is that the relevant "flow" occurs in the time dimension, (i.e. where should a mass go over time given the nature of spacetime in the vicinity?), because it's nonintuitive to picture a geometrical aspect of time. I think it's fair to think of it as: the time aspect of spacetime answers "what should happen next?", and in this case the time aspect of spacetime says "masses should move towards the Earth's center of mass" or more broadly, "masses should move in the direction of the 'deepest spacetime well nearby' with the most urgency", and time says this because of the way masses warp spacetime.
Interesting thought about a stationary tree branch supplying energy to a stationary apple. We think of energy transferred as force x distance. In this case the distance is entirely through time and not space. So, is that really transfer of energy or is it something else?
Great question. This all comes down to the equivalence principle view of gravity, how an object held stationary in a gravitational field (like the apple on the branch) is equivalent to that same object accelerating in a rocket far out in space away from significant gravitational fields. If these two really are equivalent, then they are amenable to equivalent descriptions in terms of energy. For an apple accelerating far out in space, it’s clear how much energy it takes to accelerate at g for one second, it’s the apple’s kinetic energy after that second (1/2 * apple mass * g^2). The energy is delivered by the rocket’s propulsion, and the store of energy is spent by that propulsion. How about the apple on the branch? In the equivalence principle view, the branch is accelerating the apple upward at g just like the rocket’s engines (and the tree is being accelerated upward by the surface of the Earth), so the same amount of energy is needed, and it’s delivered through molecular bonds in the branch. This discussion that someone shared with me regarding this video might help clarify the situation, especially Viktor Toth’s answer: qr.ae/pGqeZl
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One more comment. Regarding that asteroid sitting in deep space. Defining "At Rest" in deep space in relation to space time, implies that there is an absolute reference frame, called Space Time. But the problem is, without another object nearby... or far away even... there is no reference to know what your velocity is. Velocity is only relevant in relationship to another object. So if two objects have differential velocity with respect to one another, which object is at rest? Or... perhaps they have 1/2 equal momentum or 1/4 and 3/4 momentum. Bottomline: What is the true spacetime reference frame?
Good question/point- I'll let this discussion on StackExchange fill in some of the details here: physics.stackexchange.com/questions/183577/is-spacetime-absolute
Quick question : is gravity canceled when you are exactly between two identical masses (like 2 planets) ? If yes, does the same happen between two black holes ? If yes again, should not that shrink the "size" of the event horizon ?
Like kara bool is saying, the effect of the gravity on you doesn't cancel out (you're pulled in both directions equally, still, so there's tension on your body), but because both influences balance each other you don't accelerate in either direction (remember that F=ma refers only to _net_ forces on an object, here with net force = 0). I believe that two black holes brought near each other would actually have their event horizons expanded in the direction pointing towards the other black hole due to its gravitational influence, but black hole physics is complicated and is decidedly above my pay grade. Interesting questions.
@@IdeaListEye Thanks to both of you. Oddly enough I have really hard time finding answers to these cases and yet it should be a study case. But if we admit that the event horizon can expend in the case above, what happens if the two black holes just pass by and don't fusion ? Will the even horizon recess once they get away from each other ? Would not that mean that something trapped behind the event horizon at that moment (just when the two BL met each other) would then be able to get out ?
My God.... Guys, dont listen to this idea dude, he has very little (to none) clue on this matter... There is nothing to "cancel out". Gravity is not a force, the only thing that matters is the so called "curvature". But since the spacetime is locally flat (relative to the size of human body), your body wouldnt feel a thing, and wouldnt be "stretched". There is no "pull" to any direction, just as there is no pull even now when you stand on the earth. You are in a free fall, inertial motion devoid of influence of any force. His video also is filled with fundamental flaws and misleading info. I mean, nothing wrong with his interest in physics, the problem is that he is trying to teach while he didnt finish the learning part. Stretched event horizons are even funnier.
@@nyalarhotep You repeated what you read in a book perfectly. Congrat. If spacetime curvature is not a "force", then what is bending spacetime ? How do we obtain an acceleration without applying a force ? And in this case, what is your definition of force ?
@@En_theo No need to be aggressive just because you failed to understand something. Be patient, read a lot, think a lot. Physics is not that hard when you take a patient and slow path. The force is external influence which alters an objects inertial movement. Gravity simply doesnt do that- free fall is inertial movement, unaltered. The space is altered. The forces dont alter space, they alter your vector inside it.
I loved this video. You helped me conceptualize the synonymity of gravity and time. Correct me if I'm wrong here but will it be plausible to say that the nature of passage of time does put a constraint on the motion of an object in space? I mean an object can move back and forth in space but it cannot move backwards in time.Additionally, why is it that the rate of 'attraction' of an object towards another massive object is constant ( for instance g= 9.8m/s²) ? Is it a sign of time being restrictive towards the motion of that object in space just because it itself has the tendency to flow at a constant rate? Can we draw such a parallel ? I would like to listen to your thoughts.
Why does an object increase its speed when it's "falling"? Something falling at eye-level of 6 ft will be much faster falling if the objects starting height was higher. As if space-time at the same location differs for objects beginning at a different "height".
This is the nature of acceleration; the longer time you spend under linear acceleration, the faster you'll be going. An object starting its fall from higher has had more time to accelerate before it passes your eye level, and that's the simple reason that object is moving faster than an object starting its fall from lower. It's not due to "space-time at the same location differs for objects beginning at a different "height""; in fact, (ignoring some infinitesimal differences), for all intents and purposes the gravitational field 100 feet up is the same as the gravitational field at 6 feet, and any object dropped from either height will be subject to effectively the same acceleration. (This description assumes that you're comfortable with the concept that masses in a gravitational field will all accelerate at the same rate due to that gravitational field, which is itself a subtle fact).
@@IdeaListEye Hello, that wasn't entirely my question sir. My question - bottom line - is: why must there be acceleration and why must it be ongoing? The latter question might be related to the first. If I drop an object (vacuum), why isn't it speed immediately 9.8 m/s and why doesn't it stay at that speed?
@@angel_machariel I see, it’s an interesting question. The easiest answer is that it's impossible for objects to discontinuously change their velocity; that is, there's no way to get from 0 m/s to 9.8 m/s without also traveling at every intervening speed between the two for an infinitesimal period. Acceleration is the term for this change over time to the object’s velocity. Note that this is even true for really fast speed changes, like a bullet going from at rest in a rifle’s chamber to going many hundreds of meters a second just milliseconds later; in the time the gunpowder explodes, the bullet first travels 1 m/s before it travels 2 m/s, and it first travels 10 m/s before it travels 100 m/s (accelerating all the while). So your question is “why is that impossible”? Any explanation for this would rely on our observations about how the Universe works, so at root the answer really is “because we’ve never observed such a thing, and everything we understand about mechanics would fall apart if that were possible”. Here’s a version of an explanation, though: in order to change an object’s speed, you have to change that object’s internal energy to kinetic energy. All energy transformations occur over time; in some way, this is what time _is_ , it’s the unfolding of energy exchanges in the Universe according to the laws of physics. Therefore changes to an object’s speed can’t occur discontinuously; i.e. if you were to look atan accelerating object over smaller and smaller slices of time, you would always find smaller and smaller slices of “change in speed”, and never find a slice of time where at the start the object has one speed, throughout the entire slice of time the object maintains that exact same speed, and at the end of the slice of time the object has jumped to a different speed.
I have always taken the views that a) spacetime emanates from every point in all directions, thus allowing for changes of direction and time and b) nucleons, which to me are almost condensed parts of spacetime with rest mass, warp it because they are impermeable and so spacetime cannot go through them, spacetime almost concertina’s up around them. Bearing in mind most solids are vacuum and when mass is really concentrated then their mass such as a black hole completely blocks spacetime as opposed to Earth which only blocks enough for us to weigh what we do at the surface. Would love to develop this further. The constant emanation is probably what we call the dark force. The emanation is what non mass waves ride along, at the speed of c. So mass is to me proportional to the volume of spacetime it encapsulates.
Nice video. Very much appreciated. But @13:15, is it that time dilation warps spacetime geodesics towards the Earth's center of mass or is it the earth's center of mass which determines the shape of these geodesics? This was stated as the main point of the video, but not enough time was spent explaining the difference between these two statements, if there is one.
Thanks! Good question. Even though this video sets out to show that the gravity we experience on earth is caused by time dilation, what I’m really trying to get across is that both are one and the same. That is, the thing we call gravity, which is the force we feel pulling us downward, is equivalent to the effect that time dilation has on the path our bodies seek to follow through spacetime. It’s not the case that one causes the other; they’re the same thing, and that single phenomenon is the result of the way mass and spacetime interact.
Mass moves in all directions equally through time relevant to the mass itself...time as a medium allows for a "vacuum effect"...it acts like a lead ball falling through water creating a vacuum as it falls...we have to find out what binds us to universal time...if static electricity binds microscopic minerals together and that accretes planetary mass that eventually warps universal time...is static-electricity...gravity? Does static-electricity affect time?
The branch provides inertial energy to stop the apple from following its geodesic path through spacetime. Where does the inertial energy come from? Is it like the surface tension of water?
Having seen all those apples and clocks move about at different rates, one question that remains is "why do objects move through time in the first place, then?"
This is a great question. Ultimately, time passes because things change. Why do things change? Because they're following the laws of physics, which require things like momentum to be conserved. Why do the laws of physics make things move, and why do things follow the laws of physics? In some way, the things have their existence rooted in and defined by the laws of physics, so you fundamentally can't separate out the laws from the things. Why do the laws and the things exist? No one knows.
Best explanation ever! I mean it. Can I make a request? In GR peoplw say spacetime has mechanical properties all its own, in this video you referred to spacetime's resistance to being warped. Can you explain a little about this? It seems very different from classical empty space!
Thank you! Happy to talk about this, fascinating question. In general, in light of GR and quantum field theory, it's wrong to think of spacetime as "nothingness", or "empty". Spacetime is a substance with well-defined properties (including a relationship to matter mediated through gravity). Nailing down the details of those properties is tricky; would it be right to say that everything is fundamentally made of the same substance, and that particles are just particular "conditions" placed on a given region of spacetime? Some would say yes (string theoreticians for example), some would say no. Those kinds of finer points are beyond our knowledge at this point.
![I.N "HALLUCINATION" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/n5B5q1Hwt_U/mqdefault.jpg)
There is a point towards the end where you say, "There comes a point where the only way to increase the speed of the object is to turn the object into light." But, I believe a better way of saying that would be, "There comes a point where the only way to increase the speed of the object is to turn the object into something with no mass."
Good point! Agreed.
Yes, it's the ultimate trade-off! Either you are at "rest" with all motion through time, or have no mass so that all motion is through space (no time passes for you).
@@ALBINO1D
Song : "No time ( left for you [ luxons ] )" by "The Guess Who"
@@2hcobda2 Bot. Reported.
@@ALBINO1D for what?
It’s almost like mass creates a hole in space that space coagulates to patch/spackle - like a hole in the wall. And that greater density of coagulating space slows down time which results in geodesics whereby the slowest time is also the lowest-energy state that an object in a gravitational field defaults to.
The man, the myth, the legend himself! Thanks for watching, Tay. I like that analogy, I think of the formation of mass as basically just this, something like a knot tied into spacetime that pulls space inwards in all directions (at the speed of light), and which in some abstract way stretches out time as well.
atoms are mostly empty space. Matter does displace space, which pushes back against the matter as it passes through it. This causes a higher density region around the mass. Essentially, gravity is the effect of spatial pressure. We aren’t pulled towards the earth, we are pushed down onto it by space. So why time dilation? Time is just the rate of quantum vibration. In a high density special field, the vibration is slowed, ergo, time is slowed.
Oh wow it actually makes sense
E=MC2 is just a joke.., First off we live in a magnetic world. E=MD (Magnetic Density), All mater is magnetic all plants people everything we know exist is magnetic. The center of a magnet will prove all this to you!! Start working with the center of a magnet and you will see many things , Anti Gravity is one.. When Tesla tested his tower in Colorado for the first time he sent too much power from space into the local power plant and blew up one of the generators. FACT.. The north and south poles are the weakest part of a magnet, The energy in the middle once you learn how to use it will blow your mind!
I have always thought of mass in this way since I was little and wondered about the stars. As I was told about gravity, I thought of it as every massive object sort of has "pushed space out of the way" to occupy that space, and that is why objects have any kind of effect on eachother to begin with.
Holy crap, I've had an amateur interest in relativity for 30 years but I've never understood gravity as a function of movement through spacetime like this before. Thanks so much, cool as hell.
I found Science Clic to be an amazing resource too. Similar descriptions: ruclips.net/video/wrwgIjBUYVc/видео.html ruclips.net/video/GQZ3R81iyE0/видео.html but there's a bunch of other videos there that are great. But I think this video indeed goes into even more detail.
I honestly think these are newer revelations. I too with 30 years of interest have never had it shown like videos these days now start to explain.
Indeed, this video is the best I found so far.
The presentation still left out issue of weight!!! He something are not very clear, but it should be accepted as their are till proof otherwise. Alright.
Because it's incorrect. Gravity is not a result of time dilation. This is a misinterpretation of correlating data.
What is offered in this video is a different description than the usual one. This is due to your starting question: what causes gravity? Answer: time dilation. And this video does a fine job in answering that question. The usual starting question from a historical perspective was: what causes time dilation? Answer: gravity. Each of these descriptions are equivalent. And that was the genius of Albert Einstein.
The clearest explanation I have ever seen. I had the 'hang on - that's obvious when you say it like that' moment. More like this pretty please..
I'm so impressed. This explains the equivalence principle. Movement due to gravity or normal acceleration impacts spacetime the same way.
Only the theory presented is supposed to do away with gravity as a force, as I understand it…
Also how is mass defined in the absence of gravity? As inertia? Sort of a resistance against acceleration?
It also seems to me that time would come out a space-vector - the path of least resistance between two locations in a three dimensional grid - which, to complicate matters further, is itself warped by all the masses in the vicinity in accordance with their masses.
Nevertheless, NASA must have precise, time proven methods by which to calculate these things. How else would they be able to slingshot objects around planetary bodies, as they often do? NASA can’t presumably rely on approximations, since last minute course-corrections would come too late, when their space probes is light-weeks away.
Couldn’t you start by covering how such calculations are done in real life before we let ourselves be overwhelmed by quantum conundrums?
Einstein described very well in the chapter "The Equality of Inertial and Gravitational Mass" of his popular book "Relativity: The Special and General Theory" the conundrum that experimentally it had been determined that inertial mass of an object is equal to its gravitational mass to a high degree of precision. Einstein's realization was that this equivalence might not be accidental. The fact that the gravitational "mass" exactly cancels out the inertial mass in the Newtonian equation for acceleration due to gravity indicates a purely geometric phenomenon behind gravitational acceleration. In other words, the "force" of gravity is fictitious, but the geometry is not what we thought it was.
@@IldarSagdejev I have the book and have read it a couple of times with great pleasure, so no!
That’s not what Einsteins says. He just states that there’s no way to discern gravitational acceleration from an equal acceleration by an equal force, unless you have some external reference, thus explaining why inertial mass and weighed mass must be one and the same.
The theory about distorting the space/time matrix came almost 20 years after Relativity was published and seems to treat time as a space-vector, which makes things more complicated to calculate, and as you know, a breakthrough usually means better and more generalized formulas.
But time, handled as a vector, must itself be distorted by mass, so how can NASA successfully calculate sling-shooting anyway?
@@Hallands.Interplanetary flight caculations use Newtonian gravity.
See "Mach's Theorem" for the possible nature of inertial mass.
this is exactly the kind of explanation i needed to understand relativity, it finally makes sense
By far the best explanatory video on the internet on the subject!! Thank you for this wonderful feeling of deeper and intuitive understanding of gravity!
Agreed, this explanation is better than the other time gradient based explanations I've seen. Thanks for taking the time to make this video.
Yes, but humans can see movement over time, we can’t see warped space.
the video belongs to another youtube channel Veritasium ... that channel just stole the video.
Disagree.
The best video about this subject I have ever seen. It's also the first time that I have the feeling that I start to understand it.
So if gravity is the difference in time dilation between 2 points that are different far away from the center of gravit, how can gravity work on an object that is flat?
The center of gravity is the center of mass. So wherever the center of mass is on the flat object will be the point of gravitation
best explanation of gravity I have seen so far
Yet it is incorrect.
Perhaps the reason that mass creates time dilation thus causing gravity is that as the universe expands the momentum of mass is holding it back from expanding at the same rate as empty space and therefore gravity.
Simplicity is the key to understanding the notion of inertial reference frames and to understand euclidian space. Cool diagrams are important and you’ve nailed it here.
I had been trying to formulate a construct about the synonynous nature of Gravity and time, which was mainly because of seeing a comment that so physicists believe that gravity is nothing but time!. That intuitively made a lot of sense to me.
What I used to think/speculate before watching this video was how time seems to be constraining the motion of an object in space and somehow making it cover a hyperbolic path which ofcourse tends to send the object towards another object.
I thought Time does it because of it being different in behaviour than than the Space coodinates. An object can move back and forth in space but cannot move backwards in time.
Additionally, time passes at a constant rate, and, any change in the movement of an object in space does change this rate of passage of time for that object!.
Your illustration of controtion of space-time in a geodesic into an energetically favourable geodesic path was new to me and helped me piece my ideas together. Thanks for the video, it was beautifully described.
I still wonder whether acceleration of an object towards another massive object being constant ( for instance g= 9.8 m/s²) is a sign of restriction of motion of an object in space because of the constant nature of passage of time.
I would love to hear your thoughts (and also correct me if I made a mistake in comprehending something).
This video answered questions that I hadn’t thought to ask. I really like your description of the “rate” at which mass warps and unwarps spacetime.
This channel must rise up! This single video filled many gaps that I've been thinking about, even after all that very same great references (PBS, Eugene, Asylum and ScienceClic). I found it searching "gravity and entropy", and I hope I can find something about it around here. Thank you!
Thanks, Gino! I'm glad you found it helpful, that's exactly what I was hoping for in making this video.
the video belongs to another youtube channel Veritasium ... that channel just stole the video.
way better and makes no room for arguments than Asylum
Excellent explanation of how gravity works. Much better than the three videos you mentioned in the beginning. I would love it if you expanded your examples of traveling through the geodesics to objects flying by a planet at different speeds. Explaining why speed matters and why traveling at different speeds determine the geodesic path of the object. At high speeds its path is slightly bent. At the right speed it winds up in orbit. At lower speeds it crashes into the planet.
Thanks! And agreed, that would be a useful illustration of how geodesics are tied to momentum.
@@IdeaListEye pls make this. there is very little research on the relation between inertial forces and geodesics.
Amazing, I've never seen it described like this! It makes so much sense to think of my inertia as me being attached to spacetime due to the way my mass warps it. Bravo
Yea that’s so believable, seems super logical, as long as you forget all knowledge ever known! Disregard everything ever felt, seen, heard, learned….-all sensible perceptions. Totally plausible! If that was no feat to overcome, then this wont be any brain-buster either…. Here soon the democrats will quit destroying the country, by funding good police and defund the wef, un, Soros, and their malnourished skinny Jeaned antifa creeps!
Outstanding video and excellent narration. Your explanation is easy to follow and very clear.
the video belongs to another youtube channel Veritasium ... that channel just stole the video.
@@Pastor_virtual_Robson Hmmm,.... and I love Derek from Veritasium. I'll look for his "original" version. thank you,
This seems like a great explanation, until you realize that: A) nothing is moving faster through time, rather the planes of simultaneity of the accelerated observers on earth are merely rotating with respect to the higher-up observers. B) the geodesics don’t “bend” into space; the ground is merely accelerating towards them, and you’re drawing them from an accelerated frame of reference C) indeed since the diagram drawn is for a uniform gravitational field, we can perform a simple coordinate transformation so that our “bent” geodesics will be straight once more, ultimately demonstrating that D) a uniform gravitational field has ZERO curvature and therefore exhibits no warping of spacetime. E) Meanwhile, a non-uniform gravitational field does have curvature; plotting this on a spacetime diagram and you would see that geodesics diverge or converge towards one another. Changing separation between geodesics is real curvature, i.e., tidal forces, which is real gravity.
It was a good video, but sorry, curved lines on a spacetime diagram do not equate to spacetime curvature.
I dont think any better video of explanation of Spacetime is available on internet. Its awesome. Very well and simplistically explained. Would like to see such videos on quantum mechanics too if by any chance u prefer to make. Thanks a lot
Thanks! Would love to make more physics-y videos, hopefully when I can find the time.
"because things pass through time at different speeds at different elevations. " I have watched HOURS of gravity RUclips videos to finally find this sentence. THANK YOU!
Finally, I’ve been trying to understand the curvature of space time for a very long time and this explanation is beautiful, this is just so amazing to me and the fact that Einstein figured all of this out on his own is amazing to me. Best explanation I’ve seen, I finally understand, thank you so much. This is so cool and it is such an amazing way to think about gravity
Einstein's work here was absolutely astounding, but he didn't do it alone! The work of his advisor, Hermann Minkowski, and the work of Lorentz were indispensable in his development of special and general relativity.
We love this video! You’re right that the connection between time dilation and gravity is only made more confusing by the “gradient flow” analogies of other videos. And we like that you’re not afraid to tackle the big questions - “why does mass warp spacetime” is the essential mystery left behind in the wake of GR. Interesting to think, for instance, that an accelerating object, in consequence of the equivalence principle, must observe a gravitational field, i.e. warped spacetime, in the vicinity of itself, and that the strength of this field is independent of both its mass and velocity.
Great work, we look forward to your future videos!
Many thanks! I hadn't heard of your channel before, but there are some really interesting topics there; looking forward to checking them out.
@@IdeaListEye Hah, we’re not big, but hit us up anytime!
"... an accelerating object, in consequence of the equivalence principle, must observe a gravitational field, i.e. warped spacetime, in the vicinity of itself, and that the strength of this field is independent of both its mass and velocity."
Well, lets do some philosophy. The only two entities in your statement that pretend to be real are the accelerating object and the act of observation of some object which is different, i.e. on the outside, from this observing and accelerating object. In this case, one may say that the observed object is the exterior, should we say the outside, of observing object. However, according to GR equivalence principle nither the accelerating object nor the gravitational field are real, therefore "the strength of this field is independent of both mass and velocity". Actually the only two real entities in your statement are the change of the rate of change, which is real because of it"s actual limit /the speed of light/ and the continuity of the extension /or the duration/. Just forget about the force and strength.
I dunno. My brother in law is really dense and warped but no one is attracted to him at all...
Maybe a sharp knife does feel attracted to him....
Maybe because of the friction.
Well attraction is relative.....generally
Well, obviously your sister married, so here go
@@Kumurajiva Nope , it was my WIFE's sister that married him.
I was commenting on a video just yesterday on how the warped 2d net in so many videos give you an incorrect picture of what is actually happening, since the warpage of spacetime would take pace in all directions at once. I give you credit for showing this warpage in a more true to life model. Thanks!
Thanks! I'd like to add that the visualization at 10:43 is by the channel ScienceClic, I neglected to include a credit there (my bad!). (Their channel is superb)
The best explanation of how time dilation is a symptom of warped spacetime which itself causes gravity (i.e. why objects accelerate towards the earth. Thank you so much as have been trying to get for over a year now 😄
This is probably the cleanest explanation I've seen in any medium. Bravo! (I had two GR courses in grad school. I've read most of the graduate-level GR textbooks, and read fairly recent research papers...and Kip Thorne's office is a few minute walk from mine). I would just point out that energy is the thing that causes time dilation somehow (energy density, more specifically). Mass just happens to be a compact form of energy. The deep connection between energy and time might be a hint pointing us toward understanding why energy density slows time.
Huge thanks, Dr. Stickley! Very much appreciated coming from you. Re. “The deep connection between energy and time might be a hint pointing us toward understanding why energy density slows time”, I’ve been playing around with the idea that spacetime warping is due to the density of particle interaction in a given region of spacetime alongside the need for relative positions and momenta needing to maintain a relativistic relationship to the speed of light. In other words, mass could be thought of as an emergent property (due to spacetime warping) that arises out of the interaction of e.g. fermions and bosons, and is not itself a fundamental property that particles (or energy) have. In simple terms, the more boson/fermion interactions, the more spacetime needs to be “knit” by those interactions into a web that maintains relative positions and momenta relative to the speed of light always being constant. The seed of this idea is the observation/hypothesis that only some interaction can define a particle’s location and trajectory in spacetime; absent these interactions, the particle exists as a spread-out “impulse” in the quantum fields, quantified in our framework by its probability amplitude.
I dug a little into particle physics to flesh this intuitive idea out and learned that I’m way out of my depth there. Something I’ll probably continue pondering, though.
@@IdeaListEye The current standard explanation for what creates mass is the Higgs mechanism; things acquire mass by interacting with the Higgs field, but this interaction is only responsible for a small part of a particle's mass; it's enough to keep the particle from moving around at c like a massless particle, but most of the measured mass of a particle comes from field energy (i.e., the swarm of virtual particles) around the particle. For an electron, most of the mass is due to energy in the electromagnetic field, since electrons have electric charge which binds to the electromagnetic field; for a quark, the mass is mostly due to the energy in the gluon field, since quarks have color charge which binds to the gluon field. The mass of composite particles, like protons is mostly due to the kinetic energy of the quarks it contains, plus the energy stored the gluon field and electromagnetic field.
Some people think that inertia may be due to the Unruh effect. I've been in favor of that general view since high school. This seems pretty similar to what you've been thinking about. Do a Google search for "is inertia due to the unruh effect?" to find out more.
I've also been playing with the idea that the rate of time passage in a region of space is somehow inversely related to the density of interactions in that region of space. I haven't been able to flesh it out into an actual theory, though. If it can be done, then gravity emerges as a direct consequence, so it would be a big deal.
You might also find "loop quantum gravity" to be interesting....there are some interesting ideas there, even if it doesn't turn out to be the way nature works.
I've watched soo many videos about general relativity. Those may have planted some seeds, but these 10 minutes made a bigger impact on my understanding than the many hours that preceded them.
Thanks for this.
I found your explanation much easier to follow that the video Space Time did on this same topic. 👍
Beautiful, it shows a dynamic space product of the energetic presence (see the previous comment for the quantum approach), so gravity potential energy is equivalent to the kinetic energy of speed √[2GM/R], Schwarzschild time dilation is equivalent exact to Lorentz dilation. The relativistic view is the union of observable speed plus the equivalent gravitational speed! This and more can be read in a small amazon book "Space, main actor of quantum and relativistic theories". Thanks for your great videos
One thing I wished you had explained regards the stumbling block I had when I first tried to understand time dilation. I could not get my mind around the fact that two old school mechanical clocks would show different times when one was moved away from the earth. It seemed like they made a mistake as the mechanical mechanism should give the same result. The glossing over the reason this happens at an atomic level is not usually explained and causes a headache when trying to put the whole picture together. Maybe a topic for a future video? André in Sydney
This has been a consideration from the start, and a lot of very smart people have taken great pains to address it (and to test what you proposed, whether it's just a mechanical accident or actually a consequence of fundamental physics). You can read more here: en.wikipedia.org/wiki/Experimental_testing_of_time_dilation
I have spent so many pleasant hours thinking about this much like you have shown here. But the second part of it I hadn't thought about, more that I accepted that all objects follow the fastest path or the one of least resistance. Great video, thanks.
the video belongs to another youtube channel Veritasium ... that channel just stole the video.
I've had a life long obsession with this subject and have come to the same conclusion that you have. Your video however has deburred the rough edges of my thinking and really brings the idea into focus, in a way that, so far as I know, is unmatched. My only disappointment is that you didn't illustrate the mechanism in which mass causes this effect in spacetime but my forgiveness is gratuitous, being that it's a very difficult problem to solve.
@@GriuGriu64 I think its useful
Mind-bending video ! 😉
I have been looking for this visual explanation for a while, and I was not satisfied with the videos you list in your introduction.
Now I know why it takes effort to climb up stairs!
the video belongs to another youtube channel Veritasium ... that channel just stole the video.
This is the best and simple explanation of why object fall (follow geodesics) I rally enjoy it, and I really appreciate your honest approach to it.
This video should be included in the physics courses they teach in school. The best explanation of gravity on the internet.
Wow! Thank you so much for making this and explaining it so clearly. Please post more
Glad you liked it! I would like to post more, but I've been busy with other things lately. Hopefully soon- do you have any topics in mind you would like to see explored?
@@IdeaListEye I previously visualized the warping of curvature as static around the mass, rather than as a dynamic/continuous motion of being sucked in. I’ve been ruminating on.. where this spacetime goes for lack of a better phrase. It just keeps getting sucked in? Maybe not enough for a whole video but the illustrations you used were so helpful to see in 3d vs the more common 2d depiction. I also think length contract doesn’t get as much love on youtube as time dilation, been trying to understand that better.
I 've been thinking why it is so difficult to understand these notions, and came to the conclusion that the problem is not only due to our experiences, the problem is also verbal. There are no words to describe situations that fall away from our experiences and senses, which is exactly what relativity theory is doing. OR ARE THERE? Plato (and Freud in is own words) say that simple statements (words) require deep understanding. I understood what the narrator is trying to commune when I realised that all objects near a big mass (like earth) have the same ANGULAR SPEED (two words) on the space time diagram. These two words crystalized the meaning of the theory and helped me remember all the details effortless.
I have a question pls
At 6:10 you state that any forward motion in time is converted into downward motion in space.. thus motion *through space begins
I saw another video which stated that although geodesic path in curved space-time gives us a path the body will take if it moves *through space, it does not explain how the motion *through space begins (if body was already in motion *through space, it would follow that path and fall to earth).
It further explained the only reason motion *through space BEGINS is due to everything already being in motion *through space (the entire universe) and thats the reason they fall.. curved spacetime gives a path, but the motion *through spacewas already there before.. passage through time does not intitate motion *through space.
Could u please explain what is right and why?
The videos is by 'But why' channel named 'what is gravity'
Btw this was excellent video.. far better than the videos by bigger channels you mentioned. thank you ❤️
Hi Rajinder, thanks for this question and your kind remarks.
There's some ambiguity here when we talk about motion; you could either mean "motion through space", "motion through time", or "motion through spacetime". When you say "although geodesic path in curved space-time gives us a path the body will take if it moves, it does not explain how the motion begins" or "the only reason motion BEGINS..." you're talking about motion through space. A critical concept here is to understand that for masses, there's only ever motion through spacetime (and never just motion through space or just motion through time). So it is the case that everything (the entire Universe of masses) is already in motion, moving at the speed of light through spacetime. (Here's a good article that explains this point a bit: medium.com/predict/we-all-travel-through-spacetime-at-the-speed-of-light-d60cb389dfc2).
Nonetheless, if we clarify which type of motion (motion through time or motion through space), we can still speak of them as separate to clarify our discussion. It's important to understand that passage through time in the examples given in my video DOES initiate motion in space, in a sense. If you drop an object on Earth, it begins to accelerate along its geodesic specifically because it was situated in a region of spacetime where it travels faster through time than it had enough energy to sustain on its own (absent your hand holding the thing up). The "spacetime friction" this exerts on the object forces it to move along its geodesic once the outside force of your hand is removed.
I hope this helps, let me know if you have any other questions.
@@IdeaListEye That was a great article and thanks for the explanation, it cleared up a few things. I've tried correcting my original comment to remove the ambiguity.
So will it be correct to say the geodesic in space, geodesic in time and geodesic in space time mean one and the same thing(path)? Does it make any sense?
And in curved space-time if any object is in motion through time it will move along its geodesic through time which inevitably also will make the object move along its geodesic through space (since they're same, but it has to give up some of its motion through time to achieve some motion through space, like MOI, angular velocity and angular momentum relationship) and it just so happens (due to nature of spacetime curvature) that the geodesic in curved spacetime is directed towards the mass in spatial co-ordinates which is causing the curving of space-time. Could you pls tell if this understanding is correct and refine if something's wrong
Also how does time dilation causes motion through space? Like the example that top of apple goes through time faster than the bottom of Apple thus causing it to spin in some way (thats what was represented in other videos you stated) and that makes it moves through space..
Wouldn't the top part of apple just rot faster than the bottom and that would be it? No motion through space warranted
@@RAHISTILLL "So will it be correct to say the geodesic in space, geodesic in time and geodesic in space time mean one and the same thing(path)?"
This is a confusing point: there's just the geodesic in spacetime, and it's made up of a space component and a time component (and to add to the confusion, the space and time components will be weighted differently depending on who's observing the object in question). Remember that geodesic just means "shortest path", and in this context it reflects the fact that it takes extra energy to travel anywhere other than along the current geodesic. Also, a geodesic is momentum-dependent; the satellites orbiting Earth are on geodesics that take them around in loops due to their angular momentum; if they didn't have that momentum, they would plummet to the Earth. I wonder if this video might clarify: ruclips.net/video/AwhKZ3fd9JA/видео.html
"Also how does time dilation causes motion through space? Like the example that top of apple goes through time faster than the bottom of Apple thus causing it to spin in some way (thats what was represented in other videos you stated) and that makes it moves through space..
Wouldn't the top part of apple just rot faster than the bottom and that would be it? No motion through space warranted"
This question demonstrates that my video was unable to convey this concept (understandable since it's a difficult concept!), so I'll try to describe it differently here. I'm going to borrow from another reply I made to another commenter; let me know if this helps!
We need to build an understanding of how spacetime works, and to do so let’s start with special relativity, the version of Einstein’s theory that doesn’t involve gravitational fields. I’ll speak of space and time separately, but it’s always the case that these two are describing part of one thing, spacetime (similar to how I can talk about up/down and left/right in space as separate things, though it’s understood they’re forever and always part of the same thing, space).
Imagine a Universe that is entirely empty of all matter except for two clocks floating in space and moving forward through time. All masses move forward through time by default, and these clocks have never been given a push, so they’re both sitting perfectly still in space.
(As a brief aside, what does it mean to move forward through time, anyway? It means that the clocks are changing according to causal interactions laid out by the laws of physics; their atoms are vibrating, their electrons are oscillating in their orbitals, their quarks are quarking about in their protons and neutrons: a dense, dizzying frenzy of natural cause and effect interactions. At a larger scale, these interactions drive current through the clock’s battery, and larger still they actuate the ticking of the clocks through the tension and release of springs and the turning of gears (Incidentally, these interactions are mediated by the exchange of photons, packets of light, which travel at maximum speed through space and zero speed through time, which suggests a deep relationship between mass and spacetime and hints at why masses warp spacetime to begin with, but that’s a different story)).
A mass that’s sitting perfectly still in space moves through time at maximum speed. These clocks then are ticking as fast as they’ll ever tick, and are accurately recording their speed through time as they do so.
Now imagine one of the clocks has a rocket attached to it, and it’s ignited, sending that clock faster and faster in one of the spatial directions. Special relativity reveals (and you might need to do some googling here to understand why) that objects that move faster through space necessarily move slower through time. This is the nature of spacetime; you must exchange some of your speed through time if you want to move faster through space; these speeds are interconvertible. As that clock speeds up closer and closer to the speed of light through space, that clock ticks slower and slower relative to the still clock; it truly is moving more slowly through time.
Ok, so the point here is that spacetime is a peculiar sort of currency exchange for any mass’s rate of change in the Universe; if that object has put all its “motion currency” into moving through time, that object must be motionless in space, and on the other hand if that object has put all its “motion currency” into moving through space, that object must be motionless in time (and must actually be made of light and nothing else, moving at the speed of light through space).
It might not seem like it, but this relates back to your original question, “why the force of (gravitational-seeming) attraction due to time dilation?”. The way that masses like the Earth warp spacetime is peculiar: they make it so objects farther away from the mass automatically have more of their “motion currency” converted to motion through time, and objects closer to the mass automatically have more of their “motion currency” converted to motion through space (towards that mass). That’s what “warped spacetime” means: it’s referring to how much of this peculiar exchange rate is favored towards motion through time and how much of it is favored towards motion through space at any point in space. Far away from any masses way out in space, spacetime is more or less “flat”, meaning the exchange rate gives maximum pace through time, miminum pace through space. (This doesn’t mean that objects slow down through space if they enter a region like this with a given velocity, just that they won’t be sped up further by any gravitational-seeming attraction).
This peculiar warping is why clocks farther from the Earth’s surface tick faster, they’re moving faster through time due to the natural exchange rate offered by the warped spacetime. Note that this isn’t a direct interaction between the Earth and whatever happens to be nearby the Earth. Instead, the Earth interacts with spacetime in its vicinity, and its influence on spacetime in turn affects whatever objects happen to be nearby.
This was a long way to go to get to the punchline: the gravitational-seeming attraction arises because in the absence of any other force, objects in the region of spacetime warped by the Earth’s mass have to accept its “motion currency” exchange rate, their interaction with spacetime dictates it. Objects without an extra energy source must accept the “cheapest motion currency” available, which coincides with traveling along a geodesic in spacetime. Near the Earth, this means giving up faster motion in time for faster motion in space towards the Earth’s center of mass. This is because, for example, sitting on the surface of the Earth requires you to move faster in time than your “motion currency” can pay for; your body alone only has the energy to fall straight downwards in space and ever slower through time rather than travel forward in time at the rate that you are (it’s a shorter path through spacetime to fall straight downward into regions of spacetime where time moves more slowly; it’s literally a less energy-intensive direction through spacetime to go). You can only remain on the surface of the Earth because the floor provides the force to hold you up in this faster time domain. The pull you feel downwards is your mass ever trying to accept spacetime’s exchange rate and speed up downwards, slowing down through time.
@@IdeaListEye That was a very thorough explanation (although I had read it before in the comment you mentioned, it was good revision regardless). Thank you.
Sry, I think framed that question rather poorly.. of course i understand why time dilation causes sensation of gravity (i think).
What i meant to ask was in those videos (science asylum and PSB) they have this animation that shows the side of object away from the mass( let's say earth) Torquing in towards earth making the object rotate around it centre of gravity which makes it fall towards earth. I dont quite understand how does that rotation around the axis fit into the explanation that you presented here. Could you please explain that?
Also i think i understand when you say there are no geodesic in space or time individually, but through space time. Its just very weird to visualise.. would it be correct to say that "passage of time has a preferred path in the physical 3 dimension"
This is very beautiful. It has helped me a lot. Thank you so much.
Great explanation, helped me a lot. Thank you very much for making this video!
Pure gold. Brilliant way to explain it. And now I FINALLY am beginning to get it. Thanks!!
You attempted to be clear and intuitive in detail at both your space and our time, the graph puzzle links a solution, IF those historical theories where snapped together as one. Allowing a healthy questioning, without any rightous declared says. We don't get much *mass* explanations, from those other channels you mentioned on this one.
Interesting hypothesis about inertia. Why do you think the bending of spacetime would resist acceleration but not constant motion? Do you know of any analogy for such a thing in known physics?
Bending of spacetime resists acceleration, not velocity. I think this is because of time. All objects must move in time and/or space. Increases in velocity is converting relative time velocity into space velocity. At the speed of light, time does not pass in your reference frame. Put another way, one might say that inertia or velocity is caused by the passage of time. More fundamentally, the constant speed of causality causes inertia.
@@bminerrolltide I realize that that's the common understanding based on the idea that everything travels at c through spacetime (which is perhaps equivalent to saying that c is the constant speed of causality, as you say). But he's trying to go deeper than that and explain exactly why spacetime resists acceleration, so I'm asking him to complete that explanation to account for the lack of resistance to constant velocity, if that makes sense. If you have any ideas, lmk.
@@GumbyTheGreen1 yeah I think I understand what you're saying. I think bending of spacetime does in fact resist any change in position, but this resistance is balanced by the object's inertia, which is caused by "the constant passage of time." Haha sounds kinda weird to say. Put another way, as the object passes through space, spacetime bending follows the object because time is passing at the same rate as the object's velocity through space. Or put another way, the object is moving on its geodesic.
This is kind of why you can say that "time" causes gravity. More precisely you can say that gravity is caused by all objects moving through spacetime at c. The mass bends spacetime, and its constant velocity in spacetime causes spacetime bending to follow the object in space. Thus, other nearby objects are pulled along these bends in spacetime, as well (gravity).
Hey Gumby, great question! I'm glad someone asked this. First off, I should state clearly that this is purely an intuitive description and understanding (in other words I don't have a derivation for this effect, but it makes sense to me (so it should of course be taken with a grain of salt)).
In my view, constant motion is a case of "balanced" spacetime warping. In other words. as the object approaches spacetime in the forward direction (really, it should be ok to talk just about space in this case, since that's the relevant dimension, but I'll stick with spacetime), the spacetime's attractive influence on that object helps propel it forward. On the flip side, as the object recedes from spacetime in the backward direction, the spacetime's attractive influence on that object resists its forward motion. I see these two influences as balancing perfectly, leading to the observation summed up by Newton's first law (A body continues at rest or in motion in a straight line with a constant speed until acted on by an unbalanced force).
In the case of an acceleration, to understand my perspective, look at it like this: the unbalanced force on the object is asking approaching spacetime and receding spacetime to warp at a different rate, upsetting the balance described above. For example, adding speed to the object in the direction it's already traveling requires spacetime to warp in the forward direction and unwarp in the reverse direction more rapidly, which takes energy to do (related to the inherent "stiffness" of spacetime ultimately defined by the permittivity and the permeability of spacetime). That energy is now considered part of the object's kinetic energy, but it's really contained in its modified relationship with spacetime (warping/unwarping spacetime more rapidly in its direction of motion).
Hi! But why does the body choose the "shortest path" between the white lines? Does it have to do with minimizing the action (the length of the world line)?
Hi! Yes, as with all spontaneous actions in physics, it's a result of the system seeking the lowest energy state. Masses follow local geodesics because it requires the least amount of energy (i.e. the object would require extra energy to follow any of the non-geodesic paths; for example, a satellite in orbit is only able to maintain orbit because it has a lot of kinetic energy perpendicular to the geodesic provided by the Earth's mass).
I realize for the sake of explaining the principle of geodisks in space-time you have used a skyscraper extending to outer space and exaggerated the time dilation enormously between the bottom & top floors. But for an object on earth such as an apple the time difference between the top of the apple and the bottom of the apple is in nanoseconds or less. How does such a miniscule time difference translate to such a high acceleration due to gravity of 9.8m/sec^2 for the apple?
Hi Ravi, good question, and good observation (I should've made it more clear in the video that this was an extreme exaggeration, as you pointed out). It turns out that in this context, 9.8m/sec^2 is quite a modest acceleration. This is because it must be considered relative to the speed of light, 300km/sec; all objects at rest are considered as moving at the speed of light in time, and when they begin to accelerate relative to other objects, the accelerating object trades some of its speed through time for speed through space (i.e. it slows down in its motion through time). From this perspective, only a very small fraction of an object falling on Earth's speed through spacetime has been converted from the time dimension into the space dimension. Here's a great video on this point: ruclips.net/video/au0QJYISe4c/видео.html
Thanks-a-lot!
Do we know of any place where there is no gravity, or only of a place where various gravitational effects are nearly balanced?
The latter; it's not possible to find a place where there is no gravity, because gravitational influences propagate at the speed of light, and if a place is findable to us, it's only because that thing is within the observable Universe (where light can have traveled to us since the big bang). Let's say you think you found a place where there is no gravity, somewhere far out in space as distant from any stars or dust clouds as possible. The fact that you can observe that place shows that that place is affected by the Earth's gravitation (because gravitation propagates at the speed of light, and you can only have observed that place if you can look at light coming from that place and its vicinity). There would have to be exactly the same mass density in every direction from any point for 13.7 billion light years in order for that place to have perfectly balanced gravity, and then if you wait a microsecond, everything in the Universe has slightly shifted position relative to that point, and it's essentially impossible for the mass balance to stay the same over that duration. So, even though astronauts float when, e.g., in transit to the moon, they are still very much influenced by the Earth's, the Sun's, the Moon's, and the Milky Way's gravity.
@@IdeaListEye So there is always time dilation?
@@IdeaListEye A typical hypothetical example of no gravitational field is intergalactic space. How fast would a clock tick there as compared to here on Earth, within the solar system and so on?
@@IdeaListEye Obviously a clock ticks faster as it is moved farther from the earth, and presumably still faster if out the distance of, say, Neptune, as it is farther from the sun, and so on. I guess what I am getting at is, how much faster could the clock tick?
@@comic4relief Basically, yes, there's always time dilation. Wherever masses interact with spacetime (an interaction that propagates through space at the speed of light), there is time dilation. The magnitude of that time dilation varies drastically from place to place in space, from almost 0 way out in space far from any masses, to almost infinity near the surface of a black hole. So even in your hypothetical example of intergalactic space, that's not a "no gravitational field" case, it's an "infinitesimally small gravitational field" case; it's overwhelmingly likely that the gravitational gradient is nonzero everywhere in space.
A clock out in intergalactic space would tick about 1 nanosecond faster per second, so obviously the effect is quite small (it would take a billion Earth seconds for the clock out in intergalactic space to tick a billion and one seconds): hyperphysics.phy-astr.gsu.edu/hbase/Relativ/gratim.html#c4
This is of course assuming that clock is at rest relative to the Earth; if it's in motion relative to the Earth, that would result in kinetic time dilation that would change the result.
Hi, thank you, a good different window of description to time and gravity.
Just 86k views?? This video deserves to be one of the best science videos I've ever seen, so much information in such a short time, and very well and easily explained as well. You are great sir.
One request for u, please explain delayed choice and delayed choice quantum eraser and other quantum related ideas sir since you'll be able to explain them simply as well I'm sure 🙂❤️❤️❤️
Sabine Hossenfelder did a great video on the subject recently. Basically, you need to combine the interference pattern from both detectors when interpreting the result. You can’t just show the pattern from one detector which a lot of other videos do.
@@eyesopencam Thanks bro, I'll look through it 🙂❤️
Wow, thanks, Umer! Very kind of you to say. I'd like to dig into those topics, thanks for the request. I have been reading about quantum computing recently, and it's monumentally complicated and confusing-- it might be a long time before I have anything valuable to say, but stay tuned!
@@IdeaListEye will be waiting sir no matter how long 🙂
No, because it is wrong, very wrong!
"Why does mass warp spacetime?"
The simple answer to the question is: relative parallax causes infinitesimal particles moving at instantaneous velocities to "slow down" or "warp" in space. That may sound impossible, but read on. It solves a LOT of problems and makes more sense than any of the current speculations.
I have been working on this for a long time and finally figured out very recently that infinitesimal particles (no size) create mass because of a parallax effect as they pass each other in space. The particles "register" each other as moving at slower rates than themselves. The further away the other particle, the slower it appears to move.
This is exactly the same effect as two airplanes who think they are flying parallel, but within a few seconds, they quickly discover that they were on a collision course, but too late, they collide.
Now these infinitesimals can never collide (being infinitesimal), but as they pass the same point in space, each becomes attracted to the other because to both particles, their paths curve, even though neither has changed course. This relative curvature causes the particles to seek a straight line in relation to each other, forcing their paths through space to curve. As their paths diverge, they become locked by a gravitational pull as each slows down in relation to the other, shaping their path as a curve. This creates a sine wave.
Time itself emerges from the relative movement of infinitesimal particles. The particles are normally inclined to change in position without change in time (instantaneous movement through space), which is identical in appearance to a stationary particle that changes its time without changes in space (instantaneous movement through time). However, the particle moving through space instantaneously has a pathway, even though it does not trace out that pathway in time. The above-mentioned curvature occurs as two particles' paths cross in close priximity relative to the rest of the universe. But since they register a velocity of each other as slower, due to a hierarchical relationship to all other particles in the universe, their path curves together, warping space time, and both particles are slowed through spacetime, though both particles are technically moving at instantaneous velocity.
This is what I call relative parallax. Their angle in relation to each other creates a spiral wave we register as a sine wave. Any other particles in close proximity can alter the path of the first particle pair and so on, causing a change in frequency. (I believe these pairs are photons or that photons are pairs of pairs of these particles based on recent findings at the LHC and the mathematical model of a photon having two parts revealed in December, explaining their spin 1), and I am currently of the opinion that the more parallel the particles travel, the flatter the wave, while the more perpendicular they travel, the more trophs in the wave, based on how much energy is transferred by the other particles. However, I am willing to accept the opposite. I still have to model it properly.
I had found that the particles have to start out with a rest velocity of instantaneous movement, leading to causing time, spacial curvature, energy and all four forces. That does not happen with non-moving particles starting with instantaneous time. In that scenario energy has to be added, but in my scenario, time, energy, mass and gravity emerge naturally. It also satisfactorilly shows that the universe is classically deterministic without some underlying, inexplicable, spooky "quantumness". (Though this does not necessarily mean that consciousness is superdeterministic, as the parts can exceed the whole to allow conscious agency.) QM is still just probability based on group theory, not a fundamental quality of space.
Bound photons sharing and trading infinitesimals creates electromagnetism and other particles in effectively three-body systems, producing 1/2 spin. It is the destabilization of the gravitational monopoles of the bound infinitesimal particles that creates electromagnetism. The restabilization of the field with additional particles having a counter-stabilizing effect produces weak force, and the perfection of this balance produces the strong force.
So this is the way to think about uniting the forces into one grand theory. So simple and elegant. Just as scientists envisioned since the Greeks. Bravo!
How does the stationary branch provide energy to keep the attached apple from following a geodesic?
Hi Ildar, great question. This all comes down to the equivalence principle view of gravity, how an object held stationary in a gravitational field (like the apple on the branch) is equivalent to that same object accerelating in a rocket far out in space away from significant gravitational fields. If these two really are equivalent, then they are amenable to equivalent descriptions in terms of energy. For an apple accelerating far out in space, it’s clear how much energy it takes to accelerate at g for one second, it’s the apple’s kinetic energy after that second (1/2 * apple mass * g^2). The energy is delivered by the rocket’s propulsion, and the store of energy is spent by that propulsion. How about the apple on the branch? In the equivalence principle view, the branch is accelerating the apple upward at g just like the rocket’s engines (and the tree is being accelerated upward by the surface of the Earth), so the same amount of energy is needed, and it’s delivered through molecular bonds in the branch. The question of what store of energy is being depleted is more difficult. I think a more general way to ask this question is “what energy is being converted into the apple’s kinetic energy?”. In a roundabout way, it’s the interaction of mass with spacetime that supplies this energy (similar to how it’s this interaction that supplies an object in a gravitational field’s potential energy in a classical framework). The Earth’s mass interacts with spacetime to warp it at a global level, and it’s this warping that causes the apple’s geodesic to bend towards the center of the Earth. I agree with your stance (what I think your stance is) that this equivalence principle version of events is highly nonintuitive, especially when you consider it from the standpoint of the conservation of energy. This discussion that someone shared with me regarding this video might help clarify the situation, especially Viktor Toth’s answer: qr.ae/pGqeZl
Thanks for creating and posting this awesome video! I could never understand why an object released from a stationary position (like a tree branch) in a gravitational field would start moving if there is no force involved. What would give it the impetus to start moving? Now that I've seen your two-dimensional graph of warped space-time, I finally think I understand it. If I understand this correctly, the object is fixed on a geodesic position, but the geodesic fabric is changing with respect to time, thus causing the object to move through the space dimension. i hope that's more or less correct anyway.
Hey David, you're welcome! Glad it helped you out.
Re. "If I understand this correctly, the object is fixed on a geodesic position, but the geodesic fabric is changing with respect to time, thus causing the object to move through the space dimension."
I think that is more or less correct, but a better way to think about it would be to say that the object is fixed on a geodesic path, not position, because every object is always traveling through spacetime; there's no fixed position because even if it's somehow perfectly stationary in space, the object is still traveling forward through time.
Using the apple as an example, the geodesic path the apple seeks to take (its path of least energy through spacetime) has it traveling downwards due to the curvature of spacetime making every other path require more energy. It's only kept from following that path by the branch exerting a force on it away from that path (upwards). So, to be clear, it's not that the "geodesic fabric is changing with respect to time"; that geodesic is fixed by the interaction between the Earth's mass, the apple's mass, and spacetime. When attached to the branch, at every instant the apple is traveling further through spacetime than it would if it could follow its preferred downwards path because the branch is pulling it away from that path into a region where time passes more quickly (causing the apple to travel through more time than it would if it were in free fall along its geodesic). I hope that helps! Let me know if you have any questions.
@@IdeaListEye Thanks for clarifying that. I see what you mean by the object not being "fixed" on the geodesic. It is always moving through time. I hope I've got that correct now. I also think I see what you mean when you say the geodesic is fixed, not the object.
Best graphic interpretation. I got tired of the "tent and the ball" everyone else used. Its like half whats happening. Feet and hands thumbs up.
Thanks! I'd like to add that the visualization at 10:43 is by the channel ScienceClic, I neglected to include a credit there (my bad!). (Their channel is superb)
That's a great way to visualize it. Kudos on the explanation and illustrations. Very impressive.
Superbly explained.... Thanks for the effort and making things simpler to understand 👍😊
Thank You so much for this video. This is the first video I have discovered so far that explains the reason of falling of objects in a proper way. 🙃👍
the video belongs to another youtube channel Veritasium ... that channel just stole the video.
Great video, thank you... just a question though... according to equivalence principle, an object in free fall is like a floating object moving freely through its geodesic in spacetime (like the space station)... so according to my understanding, time for the falling apple should be as fast as it is for the space station until it falls on earth, at which its time will move slower... am I missing something?
I loved your description of the attraction of matter to space-time causing gravity.😀😍 Resistance to movement change from forces and gravity and geodesics. The graphic was good to imagine matter sucking in space time. It helps give an intuition for it. Your questions give us ways to think about it and your answers frame it well, for sure! (Why does it take energy to move an object from its geodesic, ie an asteroid in space.)
Thanks for this video. With such a grip on spacetime and matter/energy, you should take the next step into fleshing out how entropy and enthalpy further quantize the events of causality. Essentially, what I’m asking you to do is to connect relativistic mechanics to quantum mechanics via focusing on entropy/enthalpy and how they define the arrow of time (or as I put it, further quantize causality).
Neither the standard model nor relativity make enough sense to fully model the world without each other, which is why Einstein spent most his life seeking the bridge and it remains the holy grail of physics. From what I understand about relativity, to consider gravity/time a force mediated by spin-2 tensor bosons is… unintuitive, while to a particle physicist, it is intuitive to consider gravity/time a fundamental force mediated by force carrier particles, as included in most standard models.
It’s literally looking for a fundamental particle for time, which imo is like looking for fundamental force carriers for speed, momentum, or inertia. These all seem like composite, non-fundamental forces for which there wouldn’t be a bosonic force carrier. It seems to me like we already have all the fundamental particles we need, what we are missing is a better understanding of how they interact via enthalpy and realize entropy. That’s so far quantifiable via high level quantum mechanics that can model up to a sufficiently composite, classical degree.
Furthermore, I would interested to see if the right understanding of the connection between quantum mechanics and relativity via entropy/enthalpy could also shed a bright light on dark matter and more importantly dark energy.
Cheers, pls do this for me even if you manage to prove this all wrong
Hey JackBlackNinja, thanks for this suggestion. It's an interesting idea, but I'm not particularly qualified to confirm or deny it. I'd encourage you to flesh it out, and perhaps even make a video on your own to explore and express your idea! If you were interested in doing so and had questions, I'd be happy to help in that regard (re. video production, etc.).
@@IdeaListEye I would so much like to make a video myself but I feel like I don't have the physics prowess nor editing skills to pull it off. You did so well with this video, which itself deals with time, so was just thinkin you might be able to explore the so-called 'arrow of time' described by the 2nd law of thermodynamics, which is a macro composite of quantum phenomena called micro states. This connection between the arrow of time described by the quantum mechanics via the 2nd law and the gravity-time described by relativity seems interesting to explore. Anyway, I totally understand if it's out of your wheel house, it's certainly out of mine too!
Keep up the stellar work boss
I look forward to when someone with insight understands why mass warps space-time.
Alas, I doubt I will live long enough.
Yep, I’m searching too!!!
I was told many years ago that time closer to the centre of Earth runs faster , on the top of a mountain time runs slower . There are 5 levels or aspects of time .
I don't get one thing. You said it takes supplying energy, to move away from the geodesic. Like the apple hanging onto the tree. I also understand that according to the equivalence principle, the apple is being accelerated upwards. Both these explanations, that suggest that energy is being supplied, make me ask... where is that energy coming from? The branch can technically hold the apple forever. So how can energy just be created like this? Where is the energy being lost, to give the energy needed to hold up the apple?
Really great question, I appreciate that you’re digging into the most conceptually confusing (and potentially, challenging to the theory) point of it.
Let’s think first about the classical version of this situation. In this view, the apple has gravitational potential energy (mgh) due to its position relative to the surface of the Earth, and zero kinetic energy. If the apple falls, its potential energy is converted into kinetic energy as it accelerates downward, until it hits the ground with potential energy 0, and its kinetic energy is dissipated via heat.
Now let’s think about it from the equivalence principled “apple continuously accelerating upward” view. Here, the apple has zero gravitational potential energy (since we’re considering it as in a rocket ship out in space, away from significant gravitational effects), and the branch is accelerating it at g. Already there’s something suspicious about this setup; what if we wait for a year? Accelerating at g (9.8 m/s^2) for a year (31,536,000 seconds) would take the apple to 309,052,800 m/s, which is faster than the speed of light. This can’t be right.
This article (en.wikipedia.org/wiki/Equivalence_principle#Einstein's_statement_of_the_equality_of_inertial_and_gravitational_mass) clarifies that the equivalence principle only holds when the volume of the experiment is small enough that tidal effects and things like exceeding the speed of light can’t be observed. So the right way to look at this might be to consider the apple just over the course of one second, right after the apple breaks free of the branch. Let’s say the apple was hanging 9.8 meters above the floor of the rocket. Here, the apple’s kinetic energy in the frame starts out at 0, and it has no gravitational potential energy; only the surrounding situation involves an exchange of energy (that is, the apple’s entire environment is accelerating). From the apple’s point of view, it’s sitting still while the floor of the rocket rushes up towards it at g, and the energy of the apple is only affected when the floor collides with it.
Now if we look back at the situation on the surface of the Earth from the equivalence principle perspective, we can hopefully see more clearly what’s going on. The “gravitational potential energy” we would classically consider the apple to have has disappeared; we just have a perfectly stationary apple in an accelerating frame. The kinetic energy we also would classically ascribe to the apple after it breaks from the branch has also disappeared; again the apple is perfectly stationary, whereas the tree and ground accelerate upwards. There’s no energy exchange with the apple until the ground hits it.
Ultimately, in switching between the two pictures, we’re switching between two ways of handling energy, and it’s much more intuitive (and therefore useful) to use the classical picture and its way of tallying energy. This doesn’t mean the “accelerating frame” picture is useless, just that it isn’t helpful when modeling things in a gravitational field.
To dig in a bit further, let’s look at the rocket scenario a little closer. What is the rocket accelerating with respect to, and what is the “falling” apple stationary with respect to? The answer is spacetime. How about the surface of the Earth from the equivalence principle perspective? What is the surface of the Earth and tree accelerating with respect to, and what is the “falling” apple stationary with respect to? Again, the answer is spacetime. In both cases, energy is causing an acceleration of masses with respect to spacetime (in the former, that energy is in the form of rocket fuel burning, and in the latter, that energy is in the form of mass, that of the Earth in particular). What’s confusing here is that the rocket’s energy is being “spent”, whereas the energy of the Earth’s mass pulling in spacetime seems not to be. The energy comes from the Earth's mass's effect on spacetime (mass being equivalent to energy), and it accompanies all masses; in fact, that's where gravitation comes from in the first place, a conversion of energy from other forms into the form of mass warping spacetime. The gravitational potential energy between any two objects is due to their relative distances and the fact that bringing them closer together lowers that potential energy (and converts it to kinetic energy). The energy was "spent" in warping spacetime when that mass was formed, setting up this potential energy, (almost the same as stretching a spring between all masses everywhere).
FYI... Dialekt's channel and his series of videos debunks time dilation as the cause of gravity. He calls out PBS, Nick Lucid, Eugene, Sabine et al as all being incorrect.
Who is correct I don't know.
I believe Dialekt is correct.
I wonder if the warping of spacetime is a measure of interactions, a convergent phenomena where time dilation is relative to the number of particle interactions. E=mc² shows a higher energy system has greater mass, but from an information science perspective, a higher energy system means higher concentration of interactions, not necessarily higher energy interactions. "Time takes longer wherever more things are happening" kinda makes intuitive sense, and I see the flow of gravitation like air flowing from below a single spot in the desert; the sand is spacetime, and objects near it will tend to fall into the loose quicksand because it's shifting. I wonder if mass energy falling away from other mass energy light years away might cause dark energy, as gravity can't overcome other forces, the sum of all falling in one galaxy pulls at the spacetime between it and all others, like two quicksand pits pushing sand between them when an object falls inside.
This is an interesting brainstorm. I'm not sure how to "confirm or deny" this, but maybe an openminded theoretical physicist will chime in here at some point.
It is funny that you think the purpose of the video is to simplify what others failed to explain regarding spacetime. 😋u actually made it even harder to understand😘
😂
i finally got it with your apple example. thank you.
I didn’t…
Thank you so much for this. I was screaming at the screen while viewing the other videos you mentioned because of their darn time-flow vector that didn't seem to have anything do with spacetime (or just space). If felt like a relativistic three-card monte. So well done.
But you've given me something new that just feels wrong (not saying it is, I'm just having trouble accepting it): If it takes extra energy to warp spacetime to get the asteroid to move over, (and this makes perfect sense), once it's up to speed it will keep going with no new energy added (at least no new external energy). But the asteroid is still warping spacetime anew as it moves along. That feels like this warping and unwarping should need energy too, just like it did to get the asteroid out of the well it had formed at rest. Or at the very least, the motion would run down as energy gets used up, and of course this doesn't happen.
The direction of travel length contraction item seemed a little shoe horned in there (bare with me here, this is not meant as a critique). So I wondered if the length contraction has something to do with the asteroid being "attracted" to the spacetime it is about to move into and warp, and I just missed that connection. Or is there a length contraction gradient which would translate to a mass gradient would translate to a time gradient and we're back to what causes gravity but this time, in direction of travel; once an object is moving, or once spacetime is unwarping, does the object create its own "straight" geodesic?
That the asteroid is "attracted" to the spacetime it is about to move into (in this example), feels similar to why mass (or probably better: energy) causes a dent in spacetime. I'm hoping the answer is not "because it does" as it currently is for why mass dents spacetime.
It also feels a little like something riding a wave. The displaced spacetime behind pushes the asteroid forward - but there is an equal ridge of spacetime in front that must be overcome, so the energy supplied to ride down the hill would be the same as the energy to climb the hill in front. (unless due to motion there is now a time gradient so there is a lag between when the energy is supplied and needed.) Or is it that spacetime itself has inertia?
Again, thank you, I've been chasing the "time causes gravity" for some time now and the veil has been lifted.
Thanks! And thank you for these insightful comments, I was hoping someone would raise some of these issues.
"If it takes extra energy to warp spacetime to get the asteroid to move over, (and this makes perfect sense), once it's up to speed it will keep going with no new energy added (at least no new external energy). But the asteroid is still warping spacetime anew as it moves along. That feels like this warping and unwarping should need energy too, just like it did to get the asteroid out of the well it had formed at rest."
This is a great question. To clarify the picture, it's better to say that it takes extra energy to change the rate at which the asteroid warps spacetime, not just that it takes energy to warp spacetime. When you speed up the asteroid in the x direction, the asteroid now needs to warp more space per time in the forward x direction, and unwarp more space per time in the backwards x direction. Because mass is attracted to spacetime, the object moving through more spacetime in the x direction is more strongly attracted to spacetime in the x direction. By the same token, the object moving away from more spacetime in the backwards x direction is more strongly attracted to spacetime in the backwards x direction; the influence of the extra warping in the forward x direction and the extra unwarping in the backwards x direction cancel out, leading to a constant velocity. This is the case in any inertial frame (even for a hypothetical object that's completely still in space), the object's attraction to spacetime in every direction cancels out, leaving the object moving at a constant velocity. It takes extra energy to upset this equilibrium by causing the object to warp/unwarp extra spacetime in any direction (which results in that object picking up velocity in that direction).
One way to say this would be that the extra attraction that the mass gains to the more rapidly approaching spacetime in the forward direction is "paid for" by an extra "drag" on the mass by the more rapidly receding spacetime (which is also attracted to and attracts the mass) in the reverse direction.
I like your idea of an object moving through spacetime as similar to something riding a wave, but I disagree with the way you have it stated ("The displaced spacetime behind pushes the asteroid forward - but there is an equal ridge of spacetime in front that must be overcome, so the energy supplied to ride down the hill would be the same as the energy to climb the hill in front."). Try to imagine this wave instead like an attractive field, maybe like a magnetic field. The approaching spacetime attracts the object forward, and the receding spacetime attracts the object backwards, and the two cancel out (for any constant velocity in the absence of other forces). The thing that applying a forward force does is cause the object to be attracted to more spacetime in both the forward and backward directions per time (and thereby to travel more distance in the forward direction per time).
You're right that the bit about length contraction was a bit shoehorned in; I included it in the video because length contraction and time dilation are correlated with increased velocity through spacetime, but not because that fact gives useful explanatory value in the case we're discussing. The space contraction and time dilation that occurs for objects moving relatively faster than others can be understood better in the context of light clocks (I'll assume you're familiar, let me know if you'd like any clarification). For a light clock traveling through space faster relative to another light clock, the photons must travel farther to tick off the same amount of time (resulting in time dilation), and space also contracts in the direction of motion to accommodate this effect. This is true not just for clocks, but for all physics: in order for the equivalence principle to hold, for an experimenter traveling at 99% the speed of light, the photons involved in the electrical currents in the experimenter's neurons, in the biochemical reactions keeping them alive, and in lighting their experiments would need to travel a ludicrously long distance in the forward direction if space contraction in that direction didn't compensate (alongside time dilation). Kinetic time dilation and space contraction are required to allow objects moving near the speed of light experience the same laws of physics that objects moving at 0 speed follow.
@@IdeaListEye Thanks for the in depth response and for the respectful tone (so many of these presenters get down right nasty when you ask something) I'd like to solve time travel just to go back before they knew these ideas and give them a taste. There was always a time before we all knew.
Anyway: The befuddlement around the inertia section comes from the warped spacetime resisting being unwarped and needing energy to do that. So far so good. But then one the unbalanced force is removed the asteroid continues to anger spacetime as it unwarps the space it is in and warps the space in front, and to my thinking, the asteroid would have to expend its kinetic energy to keep that up; the warpage acting kind of like friction. Why is a body in motion more slippery than a body at rest? (with respect to the spacetime it warps)
Regarding mass's attractiveness to spacetime, based on the inflow 3D representation of this it seems like that flow would empty the universe in short order. Is this the correct way to think of it? Is this better than the idea that mass just warps spacetime instead making a sink? (so a still from that animation instead of a constant flow?) Is it a flow or a stretch?
Assuming a spheroid asteroid of even mass distribution, time dilations would be consistent all the way round, spacetime warping would be the same all the way round, I'm having trouble understanding why spacetime would being willing to unwarp and warp in the direction of travel with no added energy since it took energy to to do it in the first place from rest.
Or is it better to look at it this way:
From a geodesic point of view, instead of saying it takes energy to unwarp the space, would it be better to say it takes energy to alter the geodesic? (I think you kind of said that) For the at-rest sphere, the geodesic is as you depicted. With a push, we are angling it's geodesic over a little bit (I think) where it stays once the push is removed. On this new geodesic it's free to continue on its merry way because that is the lowest possible energy state and it's warping spacetime as it goes because, well, that's what mass does inherently. (BTW, to be clear, it's not that I doubt this happens, it's the depiction that energy is required to unwarp and warp space anew that has me frowning) As you say, if inertia is still a shoulder-shrugger even for Kip Thorne et al then there may be no answer to this.
Whether the sphere is warping spacetime while it moves or is stationary probably doesn't matter - the energy to do that is built into the mass of the object doing the warping. Does the motion really matter at all? Spacetime is reacting to the proximity of a bundle of energy and I"m not sure that needs any help or incurs an energy debt.
I love your geodesics diagrams for time causing gravity. I have now found another video that finally visualizes time and length contractions and dilations by warping the graph grid itself with the lorentz tranforms, while the spacetime motion remains the same - light bulb moment! (I prefer to get the concept before digging into the math - I came form the shut up and calculate school - I get the right answers when doing the math but I'm queasy about why. I could be wrong on this but I think Einstein made bigger leaps in the field by conceptualizing than in doing the math)
Yep savvy with light clocks. I was just thinking perhaps length contraction had something to do with how the object would be attracted to spacetime (bit of a hail mary on my part) and thought that's why that segment was there. Can't-get-puzzle-peice-to-fit!
@@markrichards5630 _"But then one the unbalanced force is removed the asteroid continues to anger spacetime as it unwarps the space it is in and warps the space in front, and to my thinking, the asteroid would have to expend its kinetic energy to keep that up; the warpage acting kind of like friction."_
The thing that "angers spacetime" (lol) is not the fact of the extra spacetime warping, it's a change to the _rate_ of spacetime warping. This is why an object way out in space resists acceleration proportional to its mass, but moves at a constant velocity (no matter how fast, up to the speed of light) in the absence of other forces. Spacetime warping at any _constant_ rate offers no resistance to motion (so it's wrong to think of it as like friction). The thing that is "frictional" is changing the _rate_ at which an object warps spacetime (which corresponds to changing the object's velocity through spacetime, i.e., accelerating it). Once you remove the unbalanced force, you're no longer changing the rate at which the object is warping spacetime, and the object/spacetime happily continue on in their new, faster interaction.
_"Regarding mass's attractiveness to spacetime, based on the inflow 3D representation of this it seems like that flow would empty the universe in short order."_
I borrowed that video representation from a great youtube video, ruclips.net/video/wrwgIjBUYVc/видео.html. Be careful in your reading of it- it's an attempt to show both space _and_ time simultaneously, and it's not showing space warping as time passes; it's instead showing inertial spacetime frames (and is a bit of a confusing picture because of that). The warping of a mass at rest far out in space is constant, and the warping of time by that mass is also constant, so there's no inflow of spacetime. The inflow applies to other masses embedded in spacetime whose geodesics have been directed by the first mass's spacetime warp towards that first mass.
_"Whether the sphere is warping spacetime while it moves or is stationary probably doesn't matter - the energy to do that is built into the mass of the object doing the warping. Does the motion really matter at all?"_
The motion definitely matters, and the nature of the sphere's warping of spacetime while it moves or is stationary _defines_ that sphere's motion (in particular, its momentum). If you believe in the conservation of momentum, the motion definitely matters. Specifically, the rate at which spacetime is warped by a moving mass (with that rate highest in its direction of motion) _is equivalent to_ that mass's momentum.
@@IdeaListEye Thanks for taking the time. This makes sense now - any disturbing of a motionless object or a constantly moving object would be an acceleration and therefor you can either look at it as that energy is needed to change the rate of motion or change the rate of warping. For my noggin I think I like the idea that the energy used to change the object's motion is in fact changing its geodesic. Is this a reasonable way to look at it? Ignoring relativistic speeds, is it safe to say that because the mass of the object doesn't change, the local shape of the curve it produces in spacetime doesn't change, and the geodesic just moves over, or, does the angle of the geodesic change too at the new constant speed?
I love how spell check turns a mangled "geodesic" into "videodisc" - I guess that's the flat-earther solution to this problem)
@@markrichards5630 That's right, the energy used to change the object's motion is changing its geodesic. This is how satellites stay in orbit: by putting in the right momentum, they now travel along a geodesic more or less parallel to the surface of the Earth.
¿La geodésica es dependiente de la velocidad no? Es decir, ¿se considera en reposo toda masa que viaja a velocidad constante?
Tienes razón, la geodésica depende de la velocidad. Ver aquí para más detalles: es.wikipedia.org/wiki/Sistema_de_referencia_inercial
Inside an atomic clock an oscillator emits about 4GHz photon that reaches a Cesium atom, which absorbs and emits about 4G photon times per second. If I place a second atomic clock near a mass the Cesium atom emits 4G - a small value of photons per second. The mass influences what? The frequency of the photon of the oscillator? The oscillation frequency of Cesium? How ? By lengthening the space between the oscillator and the atom?
Great question! I'll be honest and say I don't know the exact details here (hopefully someone more informed can chime in), and add that the interaction of particles with gravity is poorly understood (see quantum gravity for more). In general, mass warps spacetime, so the change in the metric of spacetime is why the atomic clock ticks more slowly relative to unwarped spacetime. Does that help answer your question?
Wow! I was never satisfied with the time gradient. Thanks a lot
Thank you for pointing out that there is no generally agreed upon theory for why inertia exists. I have been trying to find the answer to that question for years and no one else has simply said that "we don't know". They always just talk around the subject. I have watched pbs space time, dr lemon, and many others. Arvin an gets closer than most, but only you have just come out and said it.
What struck me was that you can imagine it time dialation ( or time contraction) as moving up the slope of the time curve, i.e. gravity is the result of the slope of the change in time dialation.
The spokes on a wheel grid analogy were fantastic. Thanks
I feel a little closer to grasping this than before I watched the video. Thank-you for sharing. A question now remains how do we effect anti-gravity?
this is the best video ive seen and it has cleared my concepts to another level. keep doing this . also share your donation link.
Thanks, SpacetimeGrid! I was having a bit of a rough day, it's really nice to hear that kind feedback, just the pick-me-up I needed! Thanks also for your idea about a donation link, I had been thinking about making one for awhile and you gave me the push I needed. Here's the link, many thanks for your support! donorbox.org/idea-list-youtube-channel
Great video but I now really don't understand why some videos say we are not attracted to the Earth but rather pushed up from it...
Great question, this is a major point of confusion on this topic. The idea that "we are not attracted to the Earth but rather pushed up from it" comes from the "equivalence principle", a hypothesis dating back 1,500 years that guided Einstein's development of general relativity. Briefly, Einstein's equivalence principle holds that the mechanism for the force experienced by someone sitting on the surface of the Earth pulling them downward is indistinguishable from the mechanism for the force experienced by someone far out in space, accelerating at g. (This is similar to how, when you enter an elevator and start accelerating upward, you feel heavier while you're accelerating; in fact, if you stood on a scale, the scale would show you weighing more while you are accelerating upward). In this sense, there should be no difference between a framework in which the Earth is attracting you downwards at g versus a framework in which the Earth is accelerating you upwards at g.
That's all well and good, but the first case is immediately intuitive to us, whereas the latter case seems ludicrous (e.g. the Earth would have to be ever expanding in every direction for this to be the case, etc.). What gives? I think the right way to look at this is that neither case is exactly true, because they aren't looking at the underlying mechanism, which is spacetime warping and your mass's interaction with that spacetime warping. So, the real story underlying both cases is that the Earth's mass interacting with spacetime warps spacetime (especially the time component of space), so that the forward direction in time for any mass has a component in the direction of the Earth's center of mass (in a sense, time is bent into the "downward" spatial dimension, and spacetime "flows" in that direction). Your mass also interacts with spacetime, and is "attached" to spacetime by that interaction. When spacetime flows towards the center of the Earth, you're attached to that flowing spacetime, and therefore your mass also is pulled along with that spacetime. The confusing part here is that the relevant "flow" occurs in the time dimension, (i.e. where should a mass go over time given the nature of spacetime in the vicinity?), because it's nonintuitive to picture a geometrical aspect of time. I think it's fair to think of it as: the time aspect of spacetime answers "what should happen next?", and in this case the time aspect of spacetime says "masses should move towards the Earth's center of mass" or more broadly, "masses should move in the direction of the 'deepest spacetime well nearby' with the most urgency", and time says this because of the way masses warp spacetime.
I hope this helps, I'm not sure if it's more or less helpful written out like this.
@@IdeaListEye thanks so much for this clarification. My confusion now lies on why mass produces this effect in space-time. Thanks to you I start understanding the consequences instead. I will focus more on the equivalence principle possible interpretations.
@@alessioandreoli2145 Why does mass produce its effect on spacetime? Now that's a great question; turns out, no one knows why that is, really. The Higgs mechanism is something of an explanation, but that kicks the ball down the road to "why do massive particles interact with the Higgs field?", which I believe is unknown. Similarly, "why do electrons interact with the electromagnetic field?" is unknown: some things are known solely from our observations about them, and not due to a more fundamental theory from which we could predict those things.
Way better and more intuitive explanation than the referenced videos at the beginning 👏👏👏
Doesn’t the spaceship bring its own gravitational field which will have a significant influence on the asteroid since it’s the ONLY gravitational field in that region of space?
Good observation that the spaceship brings its own gravitational field. However, whether or not it's the _only_ gravitational field in that region of space doesn't change how significant its influence is, which is negligible. Imagine the gravitational attraction you feel towards a large plane as you're getting ready to board; it's completely impossible to notice, because gravity is such an incredibly weak force for smaller masses like this.
@@IdeaListEye But it’s not negligible . As the ‘only’ gravitational field in this region it has a huge effect. Your comparison with a large plane is irrelevant as that plane is competing with the Earth’s gravitational field which is absent here.
@@arnesaknussemm2427 The magnitude of the gravitational force between any two masses is independent of any other gravitational forces on them. At non-relatavistic speeds, it's Newton's universal law of gravitation, F = G*(m1*m2)/r^2. In other words, there's no such thing as gravitational fields "competing" with one another to reduce the force of another gravitational field.
@@IdeaListEye I know this but the EFFECTS of a gravitational field can be cancelled or reduced by another. The Apple only falls from the tree when the effects of the electromagnetic force hitherto holding it up are reduced ie the stalk breaks allowing the much weaker gravitational force which was always acting on it to have a greater effect.
@@IdeaListEye ‘there is no such thing as gravitational fields competing with one another” errr never heard of Lagrangian points?
Awesome approach! I love finding new teachers like you. Keep it up
the video belongs to another youtube channel Veritasium ... that channel just stole the video.
@@Pastor_virtual_Robson I wrote this comment on a completely different video, not Derek's either. Weird
The casimir effect is probably related to why mass warps spacetime, I tried making a very simple abstract model of it (probably terrible way to go about it) but it would make sense, an empty region of space exerts a certain amount of force, the force pushes equally on other empty space and it cancels out giving flat curvature, as soon as any mass occupies it, it "blocks out" the things the effect emerges from and the force is no longer fully balanced out on neighboring regions of spacetime.
like there is something that props up spacetime so it is flat, like if you had a trampoline with the skin of it levitated by something that is "obsured" by mass
Would you be so kind as to explain why this method provides a estimation of geodesics? Could it be generalized? Thanks in advance.
Is tree branch continuously putting energy into the apple? I can't make sense of that claim. Any help please?
Hi Parker, great question. This all comes down to the equivalence principle view of gravity, how an object held stationary in a gravitational field (like the apple on the branch) is equivalent to that same object accerelating in a rocket far out in space away from significant gravitational fields. If these two really are equivalent, then they are amenable to equivalent descriptions in terms of energy. For an apple accelerating far out in space, it’s clear how much energy it takes to accelerate at g for one second, it’s the apple’s kinetic energy after that second (1/2 * apple mass * g^2). The energy is delivered by the rocket’s propulsion, and the store of energy is spent by that propulsion. How about the apple on the branch? In the equivalence principle view, the branch is accelerating the apple upward at g just like the rocket’s engines (and the tree is being accelerated upward by the surface of the Earth), so the same amount of energy is needed, and it’s delivered through molecular bonds in the branch. The question of what store of energy is being depleted is more difficult. I think a more general way to ask this question is “what energy is being converted into the apple’s kinetic energy?”. In a roundabout way, it’s the interaction of mass with spacetime that supplies this energy (similar to how it’s this interaction that supplies an object in a gravitational field’s potential energy in a classical framework). The Earth’s mass interacts with spacetime to warp it at a global level, and it’s this warping that causes the apple’s geodesic to bend towards the center of the Earth.
I agree with your stance (what I think your stance is) that this equivalence principle version of events is highly nonintuitive, especially when you consider it from the standpoint of the conservation of energy. This discussion that someone shared with me regarding this video might help clarify the situation, especially Viktor Toth’s answer: qr.ae/pGqeZl
Here’s also some more clarification from a similar question I was asked in another comment: The idea that "we are not attracted to the Earth but rather pushed up from it" comes from the "equivalence principle", a hypothesis dating back 1,500 years that guided Einstein's development of general relativity. Briefly, Einstein's equivalence principle holds that the mechanism for the force experienced by someone sitting on the surface of the Earth pulling them downward is indistinguishable from the mechanism for the force experienced by someone far out in space, accelerating at g. (This is similar to how, when you enter an elevator and start accelerating upward, you feel heavier while you're accelerating; in fact, if you stood on a scale, the scale would show you weighing more while you are accelerating upward). In this sense, there should be no difference between a framework in which the Earth is attracting you downwards at g versus a framework in which the Earth is accelerating you upwards at g.
That's all well and good, but the first case is immediately intuitive to us, whereas the latter case seems ludicrous (e.g. the Earth would have to be ever expanding in every direction for this to be the case, etc.). What gives? I think the right way to look at this is that neither case is exactly true, because they aren't looking at the underlying mechanism, which is spacetime warping and your mass's interaction with that spacetime warping. So, the real story underlying both cases is that the Earth's mass interacting with spacetime warps spacetime (especially the time component of space), so that the forward direction in time for any mass has a component in the direction of the Earth's center of mass (in a sense, time is bent into the "downward" spatial dimension, and spacetime "flows" in that direction). Your mass also interacts with spacetime, and is "attached" to spacetime by that interaction. When spacetime flows towards the center of the Earth, you're attached to that flowing spacetime, and therefore your mass also is pulled along with that spacetime. The confusing part here is that the relevant "flow" occurs in the time dimension, (i.e. where should a mass go over time given the nature of spacetime in the vicinity?), because it's nonintuitive to picture a geometrical aspect of time. I think it's fair to think of it as: the time aspect of spacetime answers "what should happen next?", and in this case the time aspect of spacetime says "masses should move towards the Earth's center of mass" or more broadly, "masses should move in the direction of the 'deepest spacetime well nearby' with the most urgency", and time says this because of the way masses warp spacetime.
Interesting thought about a stationary tree branch supplying energy to a stationary apple. We think of energy transferred as force x distance. In this case the distance is entirely through time and not space. So, is that really transfer of energy or is it something else?
Great question. This all comes down to the equivalence principle view of gravity, how an object held stationary in a gravitational field (like the apple on the branch) is equivalent to that same object accelerating in a rocket far out in space away from significant gravitational fields. If these two really are equivalent, then they are amenable to equivalent descriptions in terms of energy. For an apple accelerating far out in space, it’s clear how much energy it takes to accelerate at g for one second, it’s the apple’s kinetic energy after that second (1/2 * apple mass * g^2). The energy is delivered by the rocket’s propulsion, and the store of energy is spent by that propulsion. How about the apple on the branch? In the equivalence principle view, the branch is accelerating the apple upward at g just like the rocket’s engines (and the tree is being accelerated upward by the surface of the Earth), so the same amount of energy is needed, and it’s delivered through molecular bonds in the branch. This discussion that someone shared with me regarding this video might help clarify the situation, especially Viktor Toth’s answer:
qr.ae/pGqeZl
Tanks you . Please do not stop making such vidéo.
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One more comment. Regarding that asteroid sitting in deep space. Defining "At Rest" in deep space in relation to space time, implies that there is an absolute reference frame, called Space Time. But the problem is, without another object nearby... or far away even... there is no reference to know what your velocity is. Velocity is only relevant in relationship to another object. So if two objects have differential velocity with respect to one another, which object is at rest? Or... perhaps they have 1/2 equal momentum or 1/4 and 3/4 momentum. Bottomline: What is the true spacetime reference frame?
Good question/point- I'll let this discussion on StackExchange fill in some of the details here: physics.stackexchange.com/questions/183577/is-spacetime-absolute
Quick question : is gravity canceled when you are exactly between two identical masses (like 2 planets) ? If yes, does the same happen between two black holes ? If yes again, should not that shrink the "size" of the event horizon ?
Like kara bool is saying, the effect of the gravity on you doesn't cancel out (you're pulled in both directions equally, still, so there's tension on your body), but because both influences balance each other you don't accelerate in either direction (remember that F=ma refers only to _net_ forces on an object, here with net force = 0). I believe that two black holes brought near each other would actually have their event horizons expanded in the direction pointing towards the other black hole due to its gravitational influence, but black hole physics is complicated and is decidedly above my pay grade. Interesting questions.
@@IdeaListEye
Thanks to both of you. Oddly enough I have really hard time finding answers to these cases and yet it should be a study case.
But if we admit that the event horizon can expend in the case above, what happens if the two black holes just pass by and don't fusion ? Will the even horizon recess once they get away from each other ?
Would not that mean that something trapped behind the event horizon at that moment (just when the two BL met each other) would then be able to get out ?
My God.... Guys, dont listen to this idea dude, he has very little (to none) clue on this matter... There is nothing to "cancel out". Gravity is not a force, the only thing that matters is the so called "curvature". But since the spacetime is locally flat (relative to the size of human body), your body wouldnt feel a thing, and wouldnt be "stretched". There is no "pull" to any direction, just as there is no pull even now when you stand on the earth. You are in a free fall, inertial motion devoid of influence of any force. His video also is filled with fundamental flaws and misleading info. I mean, nothing wrong with his interest in physics, the problem is that he is trying to teach while he didnt finish the learning part. Stretched event horizons are even funnier.
@@nyalarhotep
You repeated what you read in a book perfectly. Congrat. If spacetime curvature is not a "force", then what is bending spacetime ? How do we obtain an acceleration without applying a force ? And in this case, what is your definition of force ?
@@En_theo No need to be aggressive just because you failed to understand something. Be patient, read a lot, think a lot. Physics is not that hard when you take a patient and slow path. The force is external influence which alters an objects inertial movement. Gravity simply doesnt do that- free fall is inertial movement, unaltered. The space is altered. The forces dont alter space, they alter your vector inside it.
I loved this video.
You helped me conceptualize the synonymity of gravity and time.
Correct me if I'm wrong here but will it be plausible to say that the nature of passage of time does put a constraint on the motion of an object in space? I mean an object can move back and forth in space but it cannot move backwards in time.Additionally, why is it that the rate of 'attraction' of an object towards another massive object is constant ( for instance g= 9.8m/s²) ? Is it a sign of time being restrictive towards the motion of that object in space just because it itself has the tendency to flow at a constant rate? Can we draw such a parallel ?
I would like to listen to your thoughts.
Why does an object increase its speed when it's "falling"? Something falling at eye-level of 6 ft will be much faster falling if the objects starting height was higher. As if space-time at the same location differs for objects beginning at a different "height".
This is the nature of acceleration; the longer time you spend under linear acceleration, the faster you'll be going. An object starting its fall from higher has had more time to accelerate before it passes your eye level, and that's the simple reason that object is moving faster than an object starting its fall from lower. It's not due to "space-time at the same location differs for objects beginning at a different "height""; in fact, (ignoring some infinitesimal differences), for all intents and purposes the gravitational field 100 feet up is the same as the gravitational field at 6 feet, and any object dropped from either height will be subject to effectively the same acceleration. (This description assumes that you're comfortable with the concept that masses in a gravitational field will all accelerate at the same rate due to that gravitational field, which is itself a subtle fact).
@@IdeaListEye Hello, that wasn't entirely my question sir. My question - bottom line - is: why must there be acceleration and why must it be ongoing? The latter question might be related to the first.
If I drop an object (vacuum), why isn't it speed immediately 9.8 m/s and why doesn't it stay at that speed?
@@angel_machariel I see, it’s an interesting question. The easiest answer is that it's impossible for objects to discontinuously change their velocity; that is, there's no way to get from 0 m/s to 9.8 m/s without also traveling at every intervening speed between the two for an infinitesimal period. Acceleration is the term for this change over time to the object’s velocity. Note that this is even true for really fast speed changes, like a bullet going from at rest in a rifle’s chamber to going many hundreds of meters a second just milliseconds later; in the time the gunpowder explodes, the bullet first travels 1 m/s before it travels 2 m/s, and it first travels 10 m/s before it travels 100 m/s (accelerating all the while).
So your question is “why is that impossible”? Any explanation for this would rely on our observations about how the Universe works, so at root the answer really is “because we’ve never observed such a thing, and everything we understand about mechanics would fall apart if that were possible”. Here’s a version of an explanation, though: in order to change an object’s speed, you have to change that object’s internal energy to kinetic energy. All energy transformations occur over time; in some way, this is what time _is_ , it’s the unfolding of energy exchanges in the Universe according to the laws of physics. Therefore changes to an object’s speed can’t occur discontinuously; i.e. if you were to look atan accelerating object over smaller and smaller slices of time, you would always find smaller and smaller slices of “change in speed”, and never find a slice of time where at the start the object has one speed, throughout the entire slice of time the object maintains that exact same speed, and at the end of the slice of time the object has jumped to a different speed.
I have always taken the views that a) spacetime emanates from every point in all directions, thus allowing for changes of direction and time and b) nucleons, which to me are almost condensed parts of spacetime with rest mass, warp it because they are impermeable and so spacetime cannot go through them, spacetime almost concertina’s up around them. Bearing in mind most solids are vacuum and when mass is really concentrated then their mass such as a black hole completely blocks spacetime as opposed to Earth which only blocks enough for us to weigh what we do at the surface. Would love to develop this further.
The constant emanation is probably what we call the dark force. The emanation is what non mass waves ride along, at the speed of c. So mass is to me proportional to the volume of spacetime it encapsulates.
Nice video. Very much appreciated. But @13:15, is it that time dilation warps spacetime geodesics towards the Earth's center of mass or is it the earth's center of mass which determines the shape of these geodesics? This was stated as the main point of the video, but not enough time was spent explaining the difference between these two statements, if there is one.
Thanks! Good question. Even though this video sets out to show that the gravity we experience on earth is caused by time dilation, what I’m really trying to get across is that both are one and the same. That is, the thing we call gravity, which is the force we feel pulling us downward, is equivalent to the effect that time dilation has on the path our bodies seek to follow through spacetime. It’s not the case that one causes the other; they’re the same thing, and that single phenomenon is the result of the way mass and spacetime interact.
Thank you! That was a very helpful explanation.
Mass moves in all directions equally through time relevant to the mass itself...time as a medium allows for a "vacuum effect"...it acts like a lead ball falling through water creating a vacuum as it falls...we have to find out what binds us to universal time...if static electricity binds microscopic minerals together and that accretes planetary mass that eventually warps universal time...is static-electricity...gravity? Does static-electricity affect time?
The branch provides inertial energy to stop the apple from following its geodesic path through spacetime. Where does the inertial energy come from? Is it like the surface tension of water?
Having seen all those apples and clocks move about at different rates, one question that remains is "why do objects move through time in the first place, then?"
This is a great question. Ultimately, time passes because things change. Why do things change? Because they're following the laws of physics, which require things like momentum to be conserved. Why do the laws of physics make things move, and why do things follow the laws of physics? In some way, the things have their existence rooted in and defined by the laws of physics, so you fundamentally can't separate out the laws from the things. Why do the laws and the things exist? No one knows.
Best explanation ever! I mean it. Can I make a request? In GR peoplw say spacetime has mechanical properties all its own, in this video you referred to spacetime's resistance to being warped. Can you explain a little about this? It seems very different from classical empty space!
Thank you! Happy to talk about this, fascinating question. In general, in light of GR and quantum field theory, it's wrong to think of spacetime as "nothingness", or "empty". Spacetime is a substance with well-defined properties (including a relationship to matter mediated through gravity). Nailing down the details of those properties is tricky; would it be right to say that everything is fundamentally made of the same substance, and that particles are just particular "conditions" placed on a given region of spacetime? Some would say yes (string theoreticians for example), some would say no. Those kinds of finer points are beyond our knowledge at this point.
@IdeaListEye Yeah! Beyond our knowledge! Please make a video about it! Thanks again.